CPH Sample Exam 128 Questions with Verified Answers
Which one of the following items does not represent the value of biostatistics in the assessment of health problems of the population and determine their extent?
...
CPH Sample Exam 128 Questions with Verified Answers
Which one of the following items does not represent the value of biostatistics in the assessment of health problems of the population and determine their extent?
(A) Finding patterns in the collected data
(B) Summarizing and presenting the information to best describe the target population
(C) Deciding what information to gather to help identify the health problems
(D) Accounting for possible inaccuracies in responses and measurements - CORRECT ANSWER (D) Accounting for possible inaccuracies in responses and measurements
A biostatistician's responsibility within a collaborating research team is to aid in the research design, analysis, and interpretation of the data. (A), (B), and (C) all describe tasks that would fall within a biostatistician's expertise area. A biostatistician would not be able to account for possible inaccuracies in the data. This is because a biostatistician only has access to the information contained within the data at hand and does not have information concerning the underlying reasoning for inaccuracies in the data.
The health department is committed to protecting and promoting the health of the country's
residents. Which of the following components of a strategic plan does this statement represent?
A. objective
B. vision
C. mission
D. goal - CORRECT ANSWER C. mission
Reduce the number of teenagers who begin to smoke. Which of the following components of a
strategic plan does this statement represent?
A. goal
B. mission
C. objective
D. vision - CORRECT ANSWER A. goal
The new director of a county health department is getting acquainted with her staff. After several
weeks of observing how her two associate directors supervise their subordinates, she notes
striking differences in their management styles.
One associate director manages employees by assuming that they are highly motivated. He
tells members of his staff that they can time-shift their work hours to accommodate their family
schedules as long as they get their work done. This director's approach to management
exemplifies which of the following leadership theories?
A. Contingency theory
B. House's path goal theory
C. McGregor's theory Y
D. Theory Z - CORRECT ANSWER C. McGregor's theory Y
The other associate director assumes that employees find no satisfaction in their work and are
exclusively motivated by their salaries. This associate director's approach to management
exemplifies which of the following leadership theories?
A. McGregor's theory
B. Contingency theory
C. Theory Z
D. House's path goal therapy - CORRECT ANSWER A. McGregor's theory
The director wants to adopt a management strategy that will meet the needs of all personnel in
her department, including the two associate directors and their diverse staffs and
responsibilities. The most appropriate leadership style for this director is one informed by which
of the following theories?
A. Theory Z
B. McGregor's theory
C. House's path to goal therapy
D. Contingency therapy - CORRECT ANSWER D. Contingency therapy
A community-based study of a program to increase physical activity is conducted, and the
findings are evaluated. A small p-value with an estimate is reported. Which of the following
is the best interpretation of this result?
A. It is likely the estimate differs from the true value because of bias.
B. It is likely the estimate differs randomly and systematically from the norm.
C. It is unlikely the estimate differs from the average because of chance.
D. It is unlikely the estimate differs from the null value because of random variability - CORRECT ANSWER D. It is unlikely the estimate differs from the null value because of random variability
A pilot study is conducted to examine whether a new drug effectively decreases cholesterol
levels over a 6-week period. Twelve participants are enrolled, and serum cholesterol levels
are measured before and after the 6-week treatment period. Investigators plan to use a
paired t-test to examine whether the drug was effective in reducing cholesterol levels.
The paired t-test is more appropriate for analysis of the results than a two-sample t-test for
which of the following reasons?
A. dependence between the pre-test and post-test measurements
B. potential non-normality of the responses
C. heterogeneous variances of the two groups
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D. non-randomness of the timing of the measurements - CORRECT ANSWER A. dependence between the pre-test and post-test measurements
A pilot study is conducted to examine whether a new drug effectively decreases cholesterol
levels over a 6-week period. Twelve participants are enrolled, and serum cholesterol levels
are measured before and after the 6-week treatment period. Investigators plan to use a
paired t-test to examine whether the drug was effective in reducing cholesterol levels.
Which of the following are the degrees of freedom for this paired t-test?
A. 10
B. 11
C. 12
D. 13
ANSWER B - CORRECT ANSWER B. 11
A pilot study is conducted to examine whether a new drug effectively decreases cholesterol
levels over a 6-week period. Twelve participants are enrolled, and serum cholesterol levels
are measured before and after the 6-week treatment period. Investigators plan to use a
paired t-test to examine whether the drug was effective in reducing cholesterol levels.
If the p-value were calculated to be 0.015, which of the following would be the most
appropriate interpretation of this p-value?
A. The probability of seeing results as unusual as the observed under the alternative
hypothesis is very small.
B. The probability of seeing results as unusual as the observed under the null hypothesis
very small.
C. The probability that the alternative hypothesis is false is very small.
D. The probability that the alternative hypothesis is true is very small.
ANSWER B - CORRECT ANSWER B. The probability of seeing results as unusual as the observed under the null hypothesis
very small.
Which of the following statements best describes an intent-to-treat analysis?
A. Analyses compare characteristics of participants who did and did not adhere to the
randomized treatment.
B. Analyses exclude all participants who did not adhere to the assigned randomized
treatment.
C. Analyses maintain the original randomized assignment of treatments in the definition of
intervention and control groups.
D. Analyses reorganize participants into intervention and control groups based on their
actual participation. - CORRECT ANSWER C. Analyses maintain the original randomized assignment of treatments in the definition of
intervention and control groups.
A study is conducted to examine whether elderly women in at-home care settings maintain
more cognitive ability than women who are residents of skilled nursing care facilities. Two
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groups of 30 elderly women were recruited independently: one group included women living
at home with a caregiver, and the second group included women living in skilled nursing care
facilities. The women were asked to perform a task and received scores on the execution of
the task (higher scores indicated higher cognitive functioning). Which of the following is the
most appropriate approach for analyzing these data?
A. chi-square (χ
2
) test
B. correlation analysis
C. paired t-test
D. two-sample t-test - CORRECT ANSWER D. two-sample t-test
A study is conducted to evaluate the relationship between pet ownership and having
depressive symptoms. Seventy participants are recruited. Each subject is identified as a
current pet owner or a non-pet owner. Participants are categorized as having or not having
symptoms of depression. Which of the following is the most appropriate method to evaluate
the association between pet ownership and having depressive symptoms in this population?
A. paired t-test
B. two-sample t-test
C. chi-square (χ2) test
D. correlation analysis - CORRECT ANSWER C. chi-square (χ2) test
The epidemic of methyl mercury poisoning in Minamata, Japan, in the 1950s illustrated
contamination of which of the following?
A. water
B. fish
C. soil
D. feed grain - CORRECT ANSWER B. fish
The Ministry of Health of a developing country is considering the nationwide implementation of
a test using biomarkers to screen for breast cancer. The test is delivered in health clinics in two
similar regions of the country, with the following results:
Region A Region B
Sensitivity 70% 80%
Specificity 85% 95%
The positive and negative predictive values are different between the two regions. Which of
the following is the most likely cause of the difference in the test's predictive values between
the two regions?
A. The prevalence of disease is different between the two regions.
B. The test is detecting the disease earlier in its natural history in one of the regions.
C. The test was not administered in similar conditions in the two regions.
D. Length-biased sampling has occurred. - CORRECT ANSWER C. The test was not administered in similar conditions in the two regions.
The Ministry of Health of a developing country is considering the nationwide implementation of
a test using biomarkers to screen for breast cancer. The test is delivered in health clinics in two
similar regions of the country, with the following results:
Region A Region B
Sensitivity 70% 80%
Specificity 85% 95%
Which of the following is the most likely cause of the difference in the test's sensitivity and
specificity between the two regions?
A. The test is detecting the disease earlier in its natural history in one of the regions.
B. Length-biased sampling has occurred.
C. The test was not administered in similar conditions in the two regions.
D. The prevalence of disease is different between the two regions - CORRECT ANSWER D. The prevalence of disease is different between the two regions
A study investigated the effects of exposure to radioactive fallout from the Hanford Nuclear
Site in Washington State in the 1940s and 1950s and subsequent development of thyroid
cancer among persons exposed as children and adolescents. Scientists used birth data from
the study area to trace and contact subjects to participate in the study. Screening consisted of
thyroid palpation, ultrasonography of the thyroid gland, and measurement of thyroid hormone
concentrations in serum and urine. Individual thyroid radiation doses were estimated from
interview data concerning place of residence and dietary history. As a result of screening, 19
subjects were diagnosed with thyroid cancer.
Which of the following terms best describes this type of study design?
A. case-control
B. ecological
C. retrospective cohort
D. cross-sectional - CORRECT ANSWER C. retrospective cohort
A study investigated the effects of exposure to radioactive fallout from the Hanford Nuclear
Site in Washington State in the 1940s and 1950s and subsequent development of thyroid
cancer among persons exposed as children and adolescents. Scientists used birth data from
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the study area to trace and contact subjects to participate in the study. Screening consisted of
thyroid palpation, ultrasonography of the thyroid gland, and measurement of thyroid hormone
concentrations in serum and urine. Individual thyroid radiation doses were estimated from
interview data concerning place of residence and dietary history. As a result of screening, 19
subjects were diagnosed with thyroid cancer.
Which of the following is the most appropriate measure of effect for this type of study?
A. prevalence odds ratio
B. odds ratio
C. correlation coefficient
D. risk ratio - CORRECT ANSWER D. risk ratio
A study investigated the effects of exposure to radioactive fallout from the Hanford Nuclear
Site in Washington State in the 1940s and 1950s and subsequent development of thyroid
cancer among persons exposed as children and adolescents. Scientists used birth data from
the study area to trace and contact subjects to participate in the study. Screening consisted of
thyroid palpation, ultrasonography of the thyroid gland, and measurement of thyroid hormone
concentrations in serum and urine. Individual thyroid radiation doses were estimated from
interview data concerning place of residence and dietary history. As a result of screening, 19
subjects were diagnosed with thyroid cancer.
Which of the following terms is most appropriate to describe the cases of thyroid cancer
identified during the first screening in this study?
A. prevalent
B. interval
C. recurrent
D. incident - CORRECT ANSWER A. prevalent
A county public health department has prepared the annual operating budget for its childhood vaccination program. It forecasts that 90,000 children will be vaccinated, requiring a total of 48,000 hours of nursing labor at an average cost of $25 per hour and 100,000 doses of vaccination at an average cost of $1.50 per dose. Fixed costs of the vaccination program, such as administration and overhead, are estimated at $50,000. Which of the following calculations is most appropriate to obtain the forecast vaccination expense per child?
A.
(48,000 × $1.50) / 90,000
B.
(90,000 × $1.50) / 48,000
C.
(100,000 × $1.50) / 48,000
D.
(100,000 × $1.50) / 90,000 - CORRECT ANSWER D.
(100,000 × $1.50) / 90,000
A study is conducted to compare colorectal screening rates in white and African-American men. Researchers contact 50 white men and 50 African-American men older than 50 years of age by telephone and ask them if they have undergone colorectal screening. Fifty-five percent of white men and 49% of African-American men report undergoing appropriate screening. Which of the following tests is the most appropriate method of analysis of the survey data?
A.
paired t-test
B.
Pearson chi-square (X2) test
C.
two-sample t-test
D.
Spearman correlation test - CORRECT ANSWER B.
Pearson chi-square (X2) test
Which of the following terms best describes the power of a local jurisdiction to independently regulate public health, safety, and welfare?
A.
unionism
B.
home rule
C.
preemption
D.
self-administration - CORRECT ANSWER B.
home rule
Which of the following terms refers to the systematic method by which environmental exposure to a substance is quantified using information about the hazardous properties of the substance, human exposure to the substance, dose-response relationships, and risk characterization?
A.
risk management
B.
risk assessment
C.
risk communication
D.
risk control - CORRECT ANSWER B.
risk assessment
A local health department establishes a program with community outreach and clinical components that is intended to reduce the number of drug-resistant tuberculosis cases. A measure of the program's outcomes is the number of
A.
clinical visits for drug-resistant tuberculosis.
B.
community education sessions.
C.
drug-resistant tuberculosis cases.
D.
patients receiving follow-up care for drug-resistant tuberculosis. - CORRECT ANSWER C.
drug-resistant tuberculosis cases.
A group uses problem solving to reconcile underlying differences and create a win-win situation for the mutual benefit of all parties. This approach exemplifies which of the following styles of conflict management?
A.
accommodating
B.
avoiding
C.
collaborating
D.
compromising - CORRECT ANSWER C.
collaborating
According to the transtheoretical model of change, as individuals go from pre-contemplation to maintenance, "con" behavioral beliefs decrease and "pro" behavioral beliefs increase. This process is best described as which of the following?
A.
decisional balance
B.
self-liberation
C.
reinforcement management
D.
self-efficacy - CORRECT ANSWER A.
decisional balance
When a public health issue emerges for which there is no "evidence base" to suggest a response strategy, which of the following actions on the part of a public health professional is most appropriate?
A.
Defer action on the issue until further information about the appropriate intervention is available.
B.
Dismiss the issue because there is insufficient evidence to make an informed decision.
C.
Implement several different strategies at once to assess which is most effective.
D.
Invest in data collection and community-based research to build a more thorough understanding of the issue. - CORRECT ANSWER D.
Invest in data collection and community-based research to build a more thorough understanding of the issue.
A study of national patterns of smoking prevalence finds that the prevalence of women smokers is higher in countries with higher national income per capita, but lower in countries experiencing rapid economic growth. Among men, the prevalence of smoking is lower in countries with higher national per capita income, but higher in countries experiencing rapid economic growth. This finding is an example of which of the following phenomena?
A.
bias
B.
confounding
C.
interaction
D.
error - CORRECT ANSWER C.
interaction
A person states, "As an African-American male in my 60s, I am at risk for prostate cancer." Which of the following is the construct of the Health Belief Model that is best illustrated by this statement?
A.
perceived susceptibility
B.
perceived barriers
C.
perceived benefits
D.
perceived severity - CORRECT ANSWER A.
perceived susceptibility
Which of the following is a priority air pollutant regulated by the National Ambient Air Quality Standards (NAAQS)?
A.
asbestos
B.
carbon dioxide
C.
methane
D.
ozone - CORRECT ANSWER D.
ozone
A multi-state regional coalition is in place to identify successful state-level strategies for enhancing health care and other community services for children with special health needs. The coalition membership currently includes health care professionals and representatives from state departments of public health, housing, education, Medicaid, and social services. There is one remaining open seat. Which of the following representatives is most appropriate to fill the open slot?
A.
a principal from one of the region's elementary schools
B.
a member of a parent advocacy group
C.
a pediatric cardiologist
D.
a pharmacist - CORRECT ANSWER B.
a member of a parent advocacy group
Variation in rates of medical procedures by race, even when controlling for insurance status, income, age, and severity of conditions, is an example of
A.
health disparity.
B.
racism.
C.
inadequate access to health care.
D.
a high rate of uninsured individuals. - CORRECT ANSWER A.
health disparity.
Which of the following models explains the relationship between socioeconomic status and health by illustrating that health status and social standing are linked to a combination of interrelated social, cultural, psychological, and environmental factors?
A.
ecological
B.
health belief
C.
transtheoretical
D.
social influence - CORRECT ANSWER A.
ecological
Which of the following is the most accurate source of denominator data for calculating disease rates in a defined population?
A.
United States Census
B.
death certificates
C.
hospital discharge records
D.
reportable infectious disease reports - CORRECT ANSWER A.
United States Census
The theory of reasoned action is a model of health behavior targeted at which of the following levels?
A.
community
B.
global
C.
individual
D.
organizational - CORRECT ANSWER C.
individual
The association between disease status and exposure for a sample from a population is as follows:
Exposed Not Exposed Total
Diseased 50 400 450
Not Diseased 50 5000 5050
Total 100 5400 5500
Which of the following is the estimated ratio of the odds of disease in the exposed versus unexposed groups?
A.
(50 / 450) ÷ (50 / 5,050)
B.
(50 / 50) ÷ (400 / 5,000)
C.
(50 / 5,050) ÷ (50 / 450)
D.
(400 / 5,400) ÷ (50 / 100) - CORRECT ANSWER B.
(50 / 50) ÷ (400 / 5,000)
Assume that the true odds ratio between an exposure and a disease is 2.7. Which of the following results in an observed odds ratio that is weaker than the true odds ratio?
A.
decreased ability to diagnose disease in unexposed individuals compared with exposed individuals
B.
failure of the unexposed individuals to participate in the study
C.
lower prevalence of exposure in control participants than in the total control population
D.
poor-quality exposure information that introduces random error into the exposure classification - CORRECT ANSWER D.
poor-quality exposure information that introduces random error into the exposure classification
Which of the following best describes the elasticity of demand for health care in the United States?
A.
perfectly elastic
B.
perfectly inelastic
C.
relatively elastic
D.
relatively inelastic - CORRECT ANSWER D.
relatively inelastic
Which of the following categories is officially sanctioned by the United States federal government with regard to describing ethnicity?
A.
American Indian or Alaska Native
B.
Asian or White
C.
Black or African-American
D.
Hispanic or Latino - CORRECT ANSWER D.
Hispanic or Latino
A health behaviors survey conducted in a large urban area includes a question about whether a person is a smoker. The company conducting the survey decides to increase the size of its random sample of survey participants from 1,500 people to approximately 20,000 people. This change will most likely have which of the following effects?
A.
increasing the standard error of the estimate
B.
decreasing the variability of the estimate
C.
no effect on survey statistics because the population size is the same
D.
increasing the confidence interval width for the parameter - CORRECT ANSWER B.
decreasing the variability of the estimate
On the basis of the present evidence, the greatest reduction in injuries and death related to motor vehicles in the United States is most likely to be a result of which of the following?
A.
increase in law enforcement and highway patrol officers
B.
stricter motor vehicle inspection laws
C.
modifications to vehicles and highway systems
D.
stiffer penalties for drunk drivers and repeat speeders - CORRECT ANSWER C.
modifications to vehicles and highway systems
A public health worker is charged with investigating family violence in a community of nearly 1 million residents. The worker uses principles of systems theory in her approach. She incorporates individuals, groups, and their environments. Which of the following terms best describes this concept?
A.
community psychology
B.
demography
C.
ethnobiology
D.
social ecology - CORRECT ANSWER D.
social ecology
Which of the following is a characteristic of a health care system based on social justice?
A.
Access to medical care is viewed as an economic reward of personal effort and achievement.
B.
Production and distribution of health care are determined by market-based demand.
C.
An individual's ability to pay is considered inconsequential for receiving medical care.
D.
Markets are assumed to be more efficient than government at allocating health resources equitably. - CORRECT ANSWER C.
An individual's ability to pay is considered inconsequential for receiving medical care.
Which of the following United States federal laws prohibits a public health practitioner from sharing individually identifiable health information stored on public health department computer systems?
A.
Occupational Safety and Health Act
B.
American Health Security Act
C.
Health Communications Act
D.
Health Insurance Portability and Accountability Act - CORRECT ANSWER D.
Health Insurance Portability and Accountability Act
Which of the following molecules are produced by B lymphocytes during the host response to infection?
A.
antibodies
B.
antigens
C.
enzymes
D.
hormones - CORRECT ANSWER A.
antibodies
A 22-year-old Latina woman brings her 13-month-old daughter to a health department clinic for routine well-child care. Both are enrolled in the Medicaid program. They live in an inner-city apartment building that the mother describes as "old and run down." The infant's diet consists of table foods; the principal protein sources are eggs, peanut butter, cheese, and canned tuna. Screening of the infant for which of the following conditions is recommended by the Centers for Disease Control and Prevention (CDC)?
A.
allergies and asthma
B.
pesticide exposure
C.
elevated blood lead concentration
D.
mercury poisoning - CORRECT ANSWER C.
elevated blood lead concentration
Which of the following infectious diseases results from inadequately treated drinking water?
A.
dysentery
B.
malaria
C.
plague
D.
tuberculosis - CORRECT ANSWER A.
dysentery
Which of the following organizations accredits local public health departments?
A.
American Public Health Association
B.
Centers for Disease Control and Prevention
C.
Public Health Accreditation Board
D.
state licensing boards - CORRECT ANSWER C.
Public Health Accreditation Board
Which of the following strategies is placed last in the hierarchy of controls for protecting the health of employees from workplace exposures?
A.
administrative controls (e.g., hazard communication)
B.
engineering controls (e.g., ventilation, isolation)
C.
personal protective equipment (e.g., hearing protection)
D.
substitution (e.g., product replacement) - CORRECT ANSWER C.
personal protective equipment (e.g., hearing protection)
What percentage of all spending on health in the United States is devoted to public health funding?
A.
3%
B.
11%
C.
28%
D.
52% - CORRECT ANSWER A.
3%
A study investigates the relationship of age to body mass index (BMI). A sample of individuals is selected, and age and BMI are measured. As part of the preliminary analysis, a simple linear regression of BMI on age is performed using a statistical software package. The resulting estimate of ß (beta) from the analysis output describes which of the following?
A.
coefficient of determination
B.
slope of the regression line
C.
estimate of the mean
D.
intercept of the regression line - CORRECT ANSWER B.
slope of the regression line
Which of the following is a modeling and simulation tool used to investigate stocks, flows, and feedback loops of complex problems?
A.
interactive planning
B.
operations research
C.
organizational cybernetics
D.
system dynamics - CORRECT ANSWER D.
system dynamics
A health services researcher is studying a new influenza vaccination to determine whether it should be recommended for all senior citizens. Which of the following vaccination attributes is most appropriate to evaluate first in the process of assessing the new vaccination?
A.
cost-benefit
B.
effectiveness
C.
efficacy
D.
efficiency - CORRECT ANSWER C.
efficacy
Which of the following is the largest source of radiation dose to the general public nationwide?
A.
medical use of x-rays
B.
nuclear power plants
C.
nuclear weapons testing fallout
D.
radon gas - CORRECT ANSWER D.
radon gas
Which of the following best describes the tendency for an insured person to overuse health services because he has insurance?
A.
adverse selection
B.
crowding out
C.
moral hazard
D.
risk aversion - CORRECT ANSWER C.
moral hazard
Which of the following historical events raised awareness of the need for the protection of research subjects and resulted in the 1947 creation of the International Code of Ethics for research?
A.
Nazi human experimentation
B.
Willowbrook hepatitis studies
C.
publication of the Belmont Report
D.
Tuskegee Syphilis Study - CORRECT ANSWER A.
Nazi human experimentation
Researchers ask a random sample of 1,001 adults nationwide whether they favor or oppose the legalization of marijuana. Fifty-five percent of respondents say they oppose it. If the researchers increase the sample size of the poll by a factor of 4 (to n=4,004), which of the following effects on the length of the 95% confidence interval for the proportion is most likely to be observed?
A.
It will decrease by a factor of 4.
B.
It will decrease by a factor of 2.
C.
It will increase by a factor of 2.
D.
It will increase by a factor of 4. - CORRECT ANSWER B.
It will decrease by a factor of 2.
In a community with 20,000 births in a given year, five births are premature. Which of the following values represents this in a manner that allows comparison with other populations?
A.
0.025
B.
2.5%
C.
25 per 10,000
D.
25 per 100,000 - CORRECT ANSWER D.
25 per 100,000
The introduction of sewage into a stream is most likely to cause a measurable change in which of the following ways?
A.
decrease in decomposing organic concentration
B.
increase in biochemical oxygen demand
C.
increase in dissolved oxygen concentration
D.
stabilization of biochemical oxygen demand - CORRECT ANSWER B.
increase in biochemical oxygen demand
The management of a health care facility requires staff to adhere to ethical principles and provide culturally appropriate care. The institutionalization of these values is most likely to influence which of the following aspects of health care provided by this facility?
A.
acceptability
B.
accessibility
C.
accountability
D.
adequacy - CORRECT ANSWER A.
acceptability
Which of the following is the formula for point prevalence of a disease?
A.
number of current cases ÷ number of persons in the population
B.
number of current cases ÷ number of persons who did not have the disease at the starting point of observation
C.
number of new cases ÷ number of persons who did not have the disease at the starting point of observation
D.
number of new cases ÷ number of persons in the population - CORRECT ANSWER A.
number of current cases ÷ number of persons in the population
A researcher is calculating the infant mortality rate of several states. Which of the following methods is most appropriate to use during this analysis to adjust for racial differences in infant mortality rates among the states?
A.
logistic regression
B.
direct standardization
C.
life table analysis
D.
linear regression - CORRECT ANSWER B.
direct standardization
At a town hall meeting, several residents of a community of 10,000 raise concern about plans to build a new chemical treatment plant within walking distance of local schools, day-care centers, and parks. The community needs a new treatment plant, but the residents' concerns about the environmental effect of the plant need to be addressed. The local health department is charged with developing a method whereby citizens can provide information about concerns and recommend alternative strategies. Which of the following is the most effective method of gathering this information?
A.
Conduct telephone interviews with residents.
B.
Schedule face-to-face interviews with residents.
C.
Mail surveys to a random selection of households.
D.
Organize focus groups with representatives from the community. - CORRECT ANSWER D.
Organize focus groups with representatives from the community.
Body mass index (BMI) is sometimes reported as age- and gender-specific z-scores. Such scores are best described as a function of which of the following?
A.
the individual's BMI and the mean and standard deviation of the specific population
B.
the individual's BMI and the mean and standard deviation of an entire population
C.
the individual's BMI, the mean of the specific population, and the standard deviation of an entire population
D.
the individual's BMI, the mean of an entire population, and the standard deviation of the specific population - CORRECT ANSWER A.
the individual's BMI and the mean and standard deviation of the specific population
In addition to ozone and particulates, which of the following pollutants is most likely to aggravate asthma?
A.
arsenic
B.
carbon monoxide
C.
lead
D.
sulfur dioxide - CORRECT ANSWER D.
sulfur dioxide
Requiring health care providers to report individual cases of disease as they are diagnosed to state or local health departments is an example of which of the following types of surveillance?
A.
active surveillance
B.
syndromic surveillance
C.
passive surveillance
D.
sentinel surveillance - CORRECT ANSWER C.
passive surveillance
Which of the following is the most important limitation in the use of vital statistics data for public health research?
A.
Births and deaths that occur outside of institutions are not recorded.
B.
Data collected vary substantially from state to state.
C.
Data files are not readily available to people collecting data outside the agency.
D.
Variables of research interest may not be collected. - CORRECT ANSWER D.
Variables of research interest may not be collected.
A federal law is passed requiring labeling on food products. In subsequent years, the rate of obesity among adults decreases. Which of the following terms best describes the relationship between the law and the change in obesity rates?
A.
causal
B.
correlated
C.
retrospective
D.
prospective - CORRECT ANSWER B.
correlated
Vaccination against polio provides lifelong protection, whereas influenza vaccines have to be administered each year. Which of the following statements best explains this difference in vaccine action?
A.
Influenza vaccines are prepared from killed viruses, but polio vaccines are prepared from live, attenuated viruses.
B.
Influenza vaccines have to be administered by injection, but the oral polio vaccine can be ingested.
C.
Influenza viruses mutate at a much higher rate than poliovirus.
D.
Poliovirus can only cause disease in humans, whereas influenza viruses can infect other species. - CORRECT ANSWER C.
Influenza viruses mutate at a much higher rate than poliovirus.
The lengths of stay for six patients were 0, 0, 1, 2, 2, and 16 days. Which is (are) the best measure(s) to summarize these data?
(A) Mean
(B) Median
(C) Median and standard deviation
(D) Mean and standard deviation
(E) Median and range - CORRECT ANSWER (E) Median and range
Because the data are skewed and have an outlier, the median and range would best summarize the data.
An epidemiologist attempts to predict the weight of an elderly person from demispan. She randomly chooses 70 elderly subjects in a particular geographic area and records their weight and demispan measurements in the form of (x i , y i ) for i = 1,. . . ,70. Given that the value of the Pearson correlation coefficient is zero, what can be deduced?
(A) There is no relation between weight and demispan
(B) There is an almost perfect relationship between weight and demispan
(C) There could be some nonlinear relationship between weight and demispan
(D) There is a strong negative relationship between weight and demispan
(E) All pairs of values of weight and demispan are practically identical - CORRECT ANSWER (C) There could be some nonlinear relationship between weight and demispan
The justification is that the Pearson correlation only looks at linear relationships. The zero value means that there is no linear relation but there could be a non linear one.
For example, if points are (-3,9),(-2,4),(-1,1), (0,0),(1,1),(2,4),(3,9), then the Pearson correlation is zero but Y=X squared.
Which of the following statistical tests is not considered a nonparametric test?
(A) Kruskal-Wallis test
(B) Wilcoxon rank-sum test
(C) Tukey's test
(D) Mann-Whitney test - CORRECT ANSWER (C) Tukey's test
There are actually two Tukey's tests. One is a post hoc procedure for ANOVA, and the other is a test for additivity used in ANOVA. Neither is a nonparametric test.
A researcher is designing a new questionnaire to examine patient stress levels on a scale of 0 to 5. What type of outcome variable is being collected?
(A) Ratio
(B) Nominal
(C) Interval
(D) Ordinal
(E) Binary - CORRECT ANSWER (D) Ordinal
Data are at the ordinal level of measurement if they can be arranged in some order, but differences between data values either cannot be determined or are meaningless.
If the chances for a second event to occur stay the same, regardless of the outcome of a first event, then the two events are:
(A) Equally likely
(B) Independent
(C) Indeterminate
(D) Mutually exclusive - CORRECT ANSWER (B) Independent
Two events A and B are independent if the occurrence of one does not affect the probability of the occurrence of the other. If A and B are not independent, they are considered dependent.
In simple linear regression, what is a method of determining the slope and intercept of the best-fitting line?
(A) Least squares
(B) R-square
(C) Minimum error
(D) Least error
(E) Regression - CORRECT ANSWER (A) Least squares
Simple linear regression involves data on a dependent variable y and one or more independent variables (x 1 , x 2 , etc.). Regression analysis involves finding the "best" mathematical model (within some restricted class of models) to describe y as a function of the x's or to predict y from the x's. The regression line is the presentation of the regression equation. Residuals are used to determine the best-fitting line, and residuals are calculated by subtracting the observed minus expected values along the regression line. A straight line satisfies the least-squares property if the sum of the squares of the residuals is the smallest sum possible.
In a group of individuals, the probability of characteristic C is 0.4, and the probability of characteristic D is 0.2. The probability of their intersection is 0.10. Which of the following statements is correct?
(A) Characteristics C and D are independent
(B) Characteristics C and D are not independent
(C) Characteristics C and D are mutually exclusive
(D) Characteristics C and D are independent and mutually exclusive
(E) Not enough information is given about the relationship between the two variables to ascertain the answer - CORRECT ANSWER (B) Characteristics C and D are not independent
Two events A and B are independent if the occurrence of one does not affect the probability of the occurrence of the other. Because there is some probability of an intersection of events, these events are not independent.
If all of the numbers in a list increase by 2, then the standard deviation is:
(A) Increased by 2
(B) Increased by 4
(C) Unchanged
(D) Cannot be determined without the actual list of numbers - CORRECT ANSWER (C) Unchanged
Adding a constant number to a list of data does not change the standard deviation, but it will change the list of numbers.
The sensitivity of a particular screening test for a disease is 95%, and the specificity is 90%. Which of the following statements is most correct?
(A) Of 100 people sampled from a population with the disease, the test will correctly detect 95 individuals as positive for the disease
(B) Of 100 people sampled from a population with the disease, the test will correctly detect 90 individuals
(C) If a person tests positive, the probability of having the disease is 0.95
(D) If a person has the disease, there is a 5% chance that the test will be negative
(E) If a person does not have the disease, there is a 5% chance that the test will be positive - CORRECT ANSWER (A) Of 100 people sampled from a population with the disease, the test will correctly detect 95 individuals as positive for the disease
Sensitivity is the proportion of truly diseased people in the screened population who are identified as diseased by the screening test. It is a measure of the probability of correctly diagnosing a case or the probability that any given case will be identified by the test (e.g., true positives). Specificity is the proportion of truly non-diseased people who are so identified by the screening test. It is a measure of the probability of correctly identifying a non-diseased person with the screening test (e.g., true negatives).
Which is the most correct statement about a scatterplot?
(A) It is used to determine whether to perform a linear regression
(B) It shows the relationship between any two variables
(C) It is used to compare the means of two variables
(D) It is a useless plot when the relationship between two variables is nonlinear
(E) It is used to investigate the relationship between two continuous variables - CORRECT ANSWER (E) It is used to investigate the relationship between two continuous variables
A scatterplot diagram is a plot of paired (x,y) data with a horizontal x-axis and a vertical y-axis. A scatterplot can be used to investigate the relationship between two continuous variables as well as to identify outliers within a data set.
The Central Limit Theorem states that:
(A) The sample mean is unbiased
(B) The sample mean is approximately normal
(C) The parent population of the sample distribution is normally distributed
(D) The sample standard deviation is approximately normal
(E) Both statements (A) and (C) can be deduced from the Central Limit Theorem - CORRECT ANSWER (B) The sample mean is approximately normal
The Central Limit Theorem states that if the sample size is large enough, the distribution of the sample means can be approximated by a normal distribution, even if the original population is not normally distributed. In other words, the distribution of the sample means approaches a normal distribution as the sample size increases.
Assume that a researcher has measured weight in a sample of 100 overweight adults before and after a diet and exercise program conducted at the local health department's weekly Eat Healthy-Be Fit community program. To determine whether the mean weight decreased six weeks after the exercise program compared to the initial baseline measures, the researcher should:
(A) Compute the correlation coefficient, r, and determine the association between being overweight and the community program
(B) Conduct a t-test for independent samples
(C) Conduct a t-test for dependent samples
(D) Conduct a chi-square test for association
(E) Not estimate the decrease because there was no control group for the program - CORRECT ANSWER (C) Conduct a t-test for dependent samples
A t-test is a hypothesis test to compare population means and proportions. In this case, the sample is dependent because the tests are performed on the same individuals in the sample.
Now assume that the researcher has measured weight in a sample of 200 overweight adults who have been randomized to receive either the diet and exercise program (cited in the previous question) or no program (i.e., to serve as a control group). All subjects are weighed at baseline and again six weeks later. Choosing from the following analysis options, which is the most appropriate way to determine whether the diet program had an impact on weight loss?
(A) Conduct an independent t-test on the six-week follow-up weight measures between the diet and exercise group and the control group
(B) Conduct a paired t-test (baseline and six-week weight) in the exercise program group and then again in the control group and compare the two P-values to determine which group had a statistically significant change
(C) Conduct a survival analysis and compute the hazard ratio to determine whether the community program is protective against weight gain
(D) Conduct an analysis of covariance using the baseline to six-week weight change scores as the dependent variable and the diet and exercise program versus control group as the independent variable
(E) Conduct an analysis of covariance using the weight at six weeks as the dependent variable, the diet and exercise program versus control group as the independent variable, and the baseline weight as a covariate - CORRECT ANSWER (E) Conduct an analysis of covariance using the weight at six weeks as the dependent variable, the diet and exercise program versus control group as the independent variable, and the baseline weight as a covariate
Analysis of covariance (ANCOVA) is a technique that involves a multiple regression model in which the study factors of interest are all treated as nominal variables. The variables being controlled for in the model (the covariates) may be measurements of any scale. We want to use the baseline weight as a covariate to adjust for, or control for, any confounding of baseline weight.
If a population has a standard deviation σ, then the standard deviation of the mean of 100 randomly selected items from this population is:
(A) σ
(B) 100 σ
(C) σ /10
(D) σ /100
(E) 0.1 - CORRECT ANSWER (C) σ/10
The standard deviation of the mean is given by: , here n = 100.
Select the most correct statement concerning relative risk and odds ratios.
(A) A relative risk of 10 has the same strength of association as a relative risk of 0.1.
(B) If the confidence interval for the relative risk does not contain 0, there is an association.
(C) It is possible to calculate a relative risk when data are from a case-control study.
(D) At least one variable should be normally distributed to calculate a relative risk.
(E) Coefficients from logistic regression analysis yield relative risk. - CORRECT ANSWER (A) A relative risk of 10 has the same strength of association as a relative risk of 0.1.
The risk ratio measures the increased risk for developing a disease after being exposed to a risk factor compared to not being exposed to the risk factor. It is given by RR = risk for the exposed/risk for the unexposed, and it is often referred to as the relative risk, which is a proportion.
Assume that a linear regression analysis is performed. Which of the following results would justify trying a different method of analysis for the data?
(A) The constant is not significant
(B) The slope coefficient = 0.001
(C) The r 2 = 0.99
(D) The r 2 = 0.001
(E) Plotting the residuals against the dependent variable gives a random cloud of points - CORRECT ANSWER (D) The r 2 = 0.001
The r 2 value indicates the amount of variance in the criterion variable Y that is accounted for by the variation in the predictor variable X. In the linear regression analysis, the set of predictor variables x 1 , x 2 , ... is used to explain variability of the criterion variable Y. The r 2 value should fall between 0 and 1, with a value closer to 1 explaining more of the variability of the model.
A type I error is defined as:
(A) The probability of rejecting the null hypothesis when the null hypothesis is true
(B) The probability of rejecting the alternative hypothesis when the null hypothesis is true
(C) The probability of rejecting the null hypothesis when the alternative hypothesis is true
(D) The probability of rejecting the alternative hypothesis when the alternative hypothesis is true - CORRECT ANSWER (A) The probability of rejecting the null hypothesis when the null hypothesis is true
This is simply the definition of type I error.
The idea that z has a standard normal distribution when is justified by:
(A) Chebyshev's Inequality
(B) Central Limit Theorem
(C) Bonferroni Inequality
(D) Box-Cox Transformation - CORRECT ANSWER (B) Central Limit Theorem
This is a standard definition. The Central Limit Theorem states that if the sum of the variables has a finite variance, then it will be approximately normally distributed.
An investigator measures a continuous variable on four independent, disjointed groups of people and would like to know whether the means of each group differ. Which statistical test should the investigator use to answer this question?
(A) Logistic regression
(B) Cox regression
(C) Chi-squared test
(D) Analysis of variance - CORRECT ANSWER (D) Analysis of variance
Analysis of variance is the only choice that is appropriate for continuous outcome variables. Logistic regression is used for binary outcomes; Cox regression is used for survival outcomes; and chi-squared tests are used for pairs of categorical variables.
An investigator would like to assess the association between two categorical variables, but a cross-tabulation of the variables reveals that some cells contain counts equal to zero. Which statistical test would be most appropriate in this situation?
(A) Scheffe's test
(B) Fisher's exact test
(C) McNemar's test
(D) Student t-test - CORRECT ANSWER (B) Fisher's exact test
Fisher's exact test is often used to test for association between two categorical variables when there are small cell counts (e.g., expected cell counts are less than or equal to 5) in a table.
The proportion of people with a disease who are correctly identified by a screening test as having the disease is called:
(A) Sensitivity
(B) Specificity
(C) Positive predictive value
(D) Negative predictive value - CORRECT ANSWER (A) Sensitivity
Sensitivity is defined as the proportion of truly diseased people in the screened population who are identified as having the disease by the screening test (true positives).
The probability that an event occurs if some condition is met is called a:
(A) Joint probability
(B) Simple probability
(C) Conditional probability
(D) Marginal probability - CORRECT ANSWER (C) Conditional probability
A conditional probability is the probability of an event assuming that another event occurred.
Which of the following does not describe a measure of the variability of a continuous variable?
(A) Standard deviation
(B) Interquartile range
(C) Confidence interval
(D) Kurtosis - CORRECT ANSWER (D) Kurtosis
In probability theory and statistics, kurtosis is a measure of the "peakedness" of the probability distribution of a real-valued random variable. Higher kurtosis means more of the variance is due to infrequent extreme deviations versus frequent modestly sized deviations.
The z-score measures the relative position of one observation relative to others in a data set. What components are needed to compute a z-score?
(A) Median and range
(B) Mean and range
(C) Mean and standard deviation
(D) Median and standard deviation - CORRECT ANSWER (C) Mean and standard deviation
A z-score measures the distance between an observation and the mean, measured in units of standard deviation.
In the construction of Box-plots, the upper and lower fences are used to detect which of the following summary?
(A) Outliers
(B) Maximum number
(C) Minimum number
(D) Quartiles - CORRECT ANSWER (A) Outliers
The lower fence is defined as: Q1 - 1.5(IQR). The upper fence is defined as: Q3 + 1.5(IQR) where Q1 and Q3 are the lower and upper quartiles and IQR is the interquartile range. The upper and lower fences are boundaries to detect any measurements beyond those fences which are called outliers.
A 911 emergency operator is flooded with calls during the daily rush hour period. What is the distribution that best describes this data set?
(A) Normal
(B) Binomial
(C) Hypergeometric
(D) Poisson - CORRECT ANSWER (D) Poisson
The Poisson distribution is used to model data that represent the number of occurrences of a specified event in a given unit of time or space.
The ability to reject the null hypothesis when the null is in fact false is called?
(A) Type I error
(B) Type II error
(C) Power
(D) Level of significance - CORRECT ANSWER (C) Power
The power of a statistical test is defined as
1-B = P (reject null | alternative is true)
A clinical experiment with four treatment groups was analyzed using an ANOVA and a significant difference in the population means is found. Which of the following is a natural next step?
(A) Tukey's or a similar method of pairwise comparison
(B) Multiple t-test comparison
(C) Check model assumptions
(D) Power analysis - CORRECT ANSWER (A) Tukey's or a similar method of pairwise comparison
Once a significant difference among the population means is found after performing an ANOVA, we next examine pairwise comparisons to further identify the nature of the differences while adjusting for the multiple comparisons via Tukey's method or a similar metho
A doctor would like to estimate a patient's weight based on their age and gender. Age and gender are known as?
(A) Response variables
(B) Dependent variables
(C) Outcome variables
(D) Independent variables - CORRECT ANSWER (D) Independent variables
In regression, the variables used to predict the response variable are independent predictor variables.
Suppose the least squares line resulting from a simple linear regression analysis between weight (y in pounds) and height (in inches) is as follows: . The interpretation of this line is: If the height is increased by 1 inch on average the weight is expected to:
(A) Increase by 4 pounds
(B) Decrease by 4 pounds
(C) Increase by 1 pound
(D) Decrease by 1 pound - CORRECT ANSWER (A) Increase by 4 pounds
The basic model in simple linear regression is given by:
y = B0 + B1X + E
and the slope
B1
can be interpreted as the change in the mean of y for a unit change in x. Here the slope is 4 thus we have an increase in weight by 4 pounds with each unit change in height.
One can describe the F-distribution as a sampling distribution of the ratio of which of the following:
(A) Two normal population means
(B) Two sample variances provided that the samples sizes are large
(C) Two normal population variances
(D) Two sample variances provided that the samples are independently drawn from two normal populations with equal variances - CORRECT ANSWER (D) Two sample variances provided that the samples are independently drawn from two normal populations with equal variances
This answer is just the definition of the F statistic which is typically used for comparing two population variances. If the parent populations are independently and normally distributed, then the F statistic is calculated by (F=var1/var2 or F=var2/var1) where the numerator is the larger of the two variances. This ratio has F-distribution with the degrees of freedom n 1 -1, n 2 -1 where n 1 and n 2 are the sample sizes.
The assumption of a t-test for the difference between the means of two independent populations is that the respective:
(A) Sample variances are equal
(B) Sample sizes are equal
(C) Populations are approximately normal
(D) Sample variances are equal, sample sizes are equal and populations are approximately normal - CORRECT ANSWER (C) Populations are approximately normal
One of the assumptions for the t-test for two independent populations is normality.
Suppose a researcher calculates a confidence interval for a population mean based on a sample size of 9. Which of the following assumptions have been made?
(A) The sampling distribution of z is normal
(B) The sampled population is approximately normal
(C) The population standard deviation is known
(D) No assumptions have been made - CORRECT ANSWER (B) The sampled population is approximately normal
In general, the assumption for a 95% confidence interval is that the mean is approximately normal since the central limit theorem will hold. However with a sample of 9 the central limit theorem will not apply and so the sampled population needs to be approximately normal.
What does the abbreviation IQR stand for?
(A) Independent query re-sampling
(B) Interrelation quantity rescaled
(C) Interquartile range
(D) Integrated quantal relation
(E) Inter-quantile relationship - CORRECT ANSWER (C) Interquartile range
The inter-quartile range is calculated by subtracting the 25th percentile of the data from the 75th percentile of the data and is used to measure variability that is not as influenced by extreme values.
The table below summarizes baseline characteristics on patients participating in a clinical trial.
Characteristic
Placebo (n=125)
Experimental (n=125)
P
Mean ( ± SD) Age
54 ± 4.5
53 ± 4.9
0.7856
% Female
39%
52%
0.0289
% Less than High School Education
24%
22%
0.0986
% Completing High School
37%
36%
% Completing Some College
39%
42%
Mean ( ± SD) Systolic Blood Pressure
136 ± 13.8
134 ± 12.4
0.4736
Mean ( ± SD) Total Cholesterol
214 ± 24.9
210 ± 23.1
0.8954
% Current Smokers
17%
15%
0.5741
% with Diabetes
8%
3%
0.0438
The following test would be used to compare mean ages between groups:
(A) Chi-square goodness of fit test
(B) Chi-square test of independence
(C) Two independent samples t test
(D) Analysis of variance - CORRECT ANSWER (C) Two independent samples t test
The outcome of interest is age, which is a continuous variable, and interest lies in comparing mean ages between two independent groups (participants assigned to the placebo as compared to participants assigned to the experimental group). The two independent samples t test is used to compare means of a continuous variable between two independent groups.
The table below summarizes baseline characteristics on patients participating in a clinical trial.
Characteristic
Placebo (n=125)
Experimental (n=125)
P
Mean ( ± SD) Age
54 ± 4.5
53 ± 4.9
0.7856
% Female
39%
52%
0.0289
% Less than High School Education
24%
22%
0.0986
% Completing High School
37%
36%
% Completing Some College
39%
42%
Mean ( ± SD) Systolic Blood Pressure
136 ± 13.8
134 ± 12.4
0.4736
Mean ( ± SD) Total Cholesterol
214 ± 24.9
210 ± 23.1
0.8954
% Current Smokers
17%
15%
0.5741
% with Diabetes
8%
3%
0.0438
The following test would be used to compare educational levels between groups:
(A) Chi-square goodness of fit test
(B) Chi-square test of independence
(C) Two independent samples t test
(D) Analysis of variance - CORRECT ANSWER (B) Chi-square test of independence
The outcome of interest is educational level, measured here as a 3-level ordinal variable, and interest lies in comparing the proportions of participants in each educational category between groups (participants assigned to the placebo as compared to participants assigned to the experimental group). The data can be organized into a 3x2 table for analysis.
The table below summarizes baseline characteristics on patients participating in a clinical trial.
Characteristic
Placebo (n=125)
Experimental (n=125)
P
Mean ( ± SD) Age
54 ± 4.5
53 ± 4.9
0.7856
% Female
39%
52%
0.0289
% Less than High School Education
24%
22%
0.0986
% Completing High School
37%
36%
% Completing Some College
39%
42%
Mean ( ± SD) Systolic Blood Pressure
136 ± 13.8
134 ± 12.4
0.4736
Mean ( ± SD) Total Cholesterol
214 ± 24.9
210 ± 23.1
0.8954
% Current Smokers
17%
15%
0.5741
% with Diabetes
8%
3%
0.0438
The following test would be used to compare prevalent diabetes between groups:
(A) Chi-square goodness of fit test
(B) Chi-square test of independence
(C) Two independent samples t test
(D) Analysis of variance - CORRECT ANSWER (B) Chi-square test of independence
The outcome of interest is prevalent diabetes status, a dichotomous or indicator variable, and interest lies in comparing the proportions of participants with diabestes between groups (participants assigned to the placebo as compared to participants assigned to the experimental group). The data can be organized into a 2x2 table for analysis.
A longitudinal cohort study is conducted to assess risk factors for diabetes. Participants free of diabetes at the start of the study are followed for 10 years for development of diabetes.
What test would be used to assess whether age is related to incident diabetes?
(A) Chi-square test of independence
(B) Two independent samples t test
(C) Analysis of variance
(D) Correlation analysis - CORRECT ANSWER (B) Two independent samples t test
The goal of the analysis is to compare mean ages (age is a continuous variable) between two independent groups (persons who develop diabetes over the 10 year follow-up as compared to those who do not).
A longitudinal cohort study is conducted to assess risk factors for diabetes. Participants free of diabetes at the start of the study are followed for 10 years for development of diabetes.
What test would be used to assess whether BMI (measured as normal weight, overweight and obese) is related to incident diabetes?
(A) Chi-square test of independence
(B) Two independent samples t test
(C) Analysis of variance
(D) Correlation analysis - CORRECT ANSWER (A) Chi-square test of independence
The outcome of interest is incident diabetes, a dichotomous or indicator variable, and the predictor is BMI. BMI is generally measured as a continuous variable, but here participants are classified into one of three ordinal categories. The goal of the analysis is to compare the proportions of participants who develop diabetes among the BMI categories. The data can be organized into a 3x2 table for analysis.
A longitudinal cohort study is conducted to assess risk factors for diabetes. Participants free of diabetes at the start of the study are followed for 10 years for development of diabetes.
What test would be used to assess whether sex is related to incident diabetes?
(A) Chi-square test of independence
(B) Two independent samples t test
(C) Analysis of variance
(D) Correlation analysis - CORRECT ANSWER (A) Chi-square test of independence
In this analysis the outcome is dichotomous (incident diabetes - yes or no) as is the predictor (sex). The data can be organized in a 2x2 table and the chi-square test of independence is used to assess whether there is a difference in the proportions of men and women who develop diabetes.
A longitudinal cohort study is conducted to assess risk factors for diabetes. Participants free of diabetes at the start of the study are followed for 10 years for development of diabetes.
Consider the study described above and suppose that the outcome is change in blood glucose level over 10 years, what test would be used to assess whether age is related to change in blood glucose level?
(A) Chi-square test of independence
(B) Two independent samples t test
(C) Analysis of variance
(D) Correlation analysis - CORRECT ANSWER (D) Correlation analysis
The goal of this analysis is to assess the relationship between two continuous variables - age and change in blood glucose level. Correlation analysis is one technique to quantify the direction (positive or negative) and strength of the association, if one exists.
A longitudinal cohort study is conducted to assess risk factors for diabetes. Participants free of diabetes at the start of the study are followed for 10 years for development of diabetes.
Consider the study described above and suppose that the outcome is change in blood glucose level over 10 years, what test would be used to assess whether BMI (measured as normal weight, overweight and obese) is related to change in blood glucose level?
(A) Chi-square test of independence
(B) Two independent samples t test
(C) Analysis of variance
(D) Correlation analysis - CORRECT ANSWER (C) Analysis of variance
The outcome of interest is change in blood glucose level, a continuous variable, and we wish to test if there is a difference in mean changes in blood glucose levels among three independent groups (persons of normal weight, overweight and obese). Analysis of variance is used to test for a difference in more than two independent means.
A longitudinal cohort study is conducted to assess risk factors for diabetes. Participants free of diabetes at the start of the study are followed for 10 years for development of diabetes.
Consider the study described above and suppose that the outcome is change in blood glucose level over 10 years, what test would be used to assess whether sex is related to change in blood glucose level?
(A) Chi-square test of independence
(B) Two independent samples t test
(C) Analysis of variance
(D) Correlation analysis - CORRECT ANSWER (B) Two independent samples t test
The outcome of interest is change in blood glucose level, a continuous variable, and we wish to test of there is a difference in mean changes in blood glucose levels between men and women (two independent groups).
A clinical trial is conducted to assess the efficacy of a new drug for increasing HDL cholesterol. A 95% confidence interval for the difference in increase in HDL cholesterol levels over 12 weeks between patients assigned to the new drug or to placebo is (-2.45, 5.97). Which of the following statements is most correct?
(A) The drug is effective in increasing HDL cholesterol
(B) There is no significant difference in HDL cholesterol levels measured at 12 weeks
(C) There is no significant difference in increases in HDL cholesterol levels measured over 12 weeks
(D) The mean increase in HDL cholesterol is substantially higher in patients receiving the new drug - CORRECT ANSWER (C) There is no significant difference in increases in HDL cholesterol levels measured over 12 weeks
The outcome of interest is the increase (or change) in HDL over 12 weeks. Because the confidence interval for the difference (between patients assigned to the new drug versus placebo) in increase in HDL includes zero (the null value), we do not have evidence of a statistically significant difference in increase in HDL between groups.
Suppose we are counting the number of patients out of 100 that have a particular disease XYZ with the probability of any one individual having the disease is 0.40.
Assuming all the patients are independent and the chance of disease is the same for each patient, what is the expected number of patients with the disease XYZ?
(A) 50
(B) 40
(C) 30
(D) 20 - CORRECT ANSWER (B) 40
Here we have a binomial experiment with 100 identical trials, and the probability of success on a single trial equals 0.40. Therefore the expected number of patients with the disease XYZ (success) is 100x.40=40.
***See #46 on Study Guide for figure***
Given the following diagram below with Group 1 (triangle) and Group 2 (diamond)
We have both scenarios produce identical pairs of group means. What factors allow the easier detection among the two group means in scenario 1 and scenario 2?
(A) Larger within group variability in scenario 1
(B) Smaller with group variability in scenario 2
(C) Smaller within group variability and larger between group variability in scenario 1
(D) Smaller within group variability and larger between group variability in scenario 2 - CORRECT ANSWER (C) Smaller within group variability and larger between group variability in scenario 1
In scenario 2 we have more variability within the groups thus causing the two groups to mix such that it is more difficult to detect the identical difference in the means. This basic example can be formalized by the analysis of variance where the total variability in an experimental situation is partition into the sums of square treatment and sums of square error.
***#47***
Based on the ANOVA table, how is the F-test computed based on the components in the ANOVA table?
Source
df
SS
MS
Treatments
k-1
SST
MST = SST/(k-1)
Error
n-k
SSE
MSE = SSE (n-1)
Total
n - 1
Total SS
(A) MST/(k - 1)
(B) MSE/(n - 1)
(C) SST/SSE
(D) MST/MSE - CORRECT ANSWER (D) MST/MSE
The test statistic for a One-way ANOVA is given by
F = MST / MSE
We reject the null hypothesis for large values of F, using a right-tailed statistical test. When the null is true, this test statistic has an F-distribution with df1= k-1 and df2= n-k.
Let S denote the sample size and P denote the population size. Which of the following statements is most correct?
(A) S can be larger or smaller than P
(B) S is always equal to P
(C) S is always smaller than or equal to P
(D) S can be larger than P - CORRECT ANSWER (C) S is always smaller than or equal to P
The sample size is a subset of the population size, thus it is always smaller than or equal to the population size.
Making inferences regarding certain characteristics of the population based on the sample data is referred to as:
(A) Random sample
(B) Statistical inference
(C) Descriptive statistics
(D) Histograms and bar charts - CORRECT ANSWER (B) Statistical inference
By definition, statistical inference is the use of statistics to make inferences concerning some unknown aspect of a population.
***See Table for #50 and #51***
A survey of 20 individuals in a rural community was asked to rate the quality of their health care program on a scale of 4 categories: excellent, good, average, and poor.
Their rating frequency distribution table is given below.
Rating
Frequency
Relative Frequency
Percent Frequency
Cumulative Relative Frequency
excellent
4
1/5
20
.20
good
*
*
*
.55
average
6
3/10
30
.85
poor
3
3/20
15
*
Total
*
*
*
Which of the following statements below is correct regarding the sum of frequencies for all categories in the above summary table?
(A) It is always equal to the number of categories in the given data set
(B) It is always equal to one
(C) It is always equal to a number between 0 and 1
(D) It is always equal to the number of individuals in the given data set - CORRECT ANSWER (D) It is always equal to the number of individuals in the given data set
A frequency distribution is a tabular summary of data showing the frequency (or number) of items in each of several nonoverlapping categories; therefore, the sum of the frequencies among all categories will always equal the number of elements (individuals) in the data set.
***See Table for #50 and #51***
A survey of 20 individuals in a rural community was asked to rate the quality of their health care program on a scale of 4 categories: excellent, good, average, and poor.
Their rating frequency distribution table is given below.
Rating
Frequency
Relative Frequency
Percent Frequency
Cumulative Relative Frequency
excellent
4
1/5
20
.20
good
*
*
*
.55
average
6
3/10
30
.85
poor
3
3/20
15
*
Total
*
*
*
The last category in a cumulative relative frequency distribution will have a cumulative relative frequency equal to?
(A) 0
(B) 1
(C) The total number of individuals in the given data set
(D) The total number of categories in the given data set - CORRECT ANSWER (B) 1
A cumulative relative frequency distribution is a tabular summary of a set of data showing the relative frequency of items less than or equal to the upper class limit of each class. The relative frequency is defined as the fraction or proportion of the total number of items. To find the cumulative relative frequencies, add all the previous relative frequencies to the relative frequency for the current row. Thus the last entry of the cumulative relative frequency column is one, indicating that one hundred percent of the data has been accumulated.
The sum of the deviations of the individual observations from their mean is?
(A) 1
(B) 0
(C) Less than 0
(D) Greater than 1 - CORRECT ANSWER (B) 0
The sum of the deviation of the individual data elements from their mean is always equal to zero. This is why we use the sum of squared deviations.
Example: 1, 3, 5, 2, 4 with mean & ***see #52 for small figure***
The probability distribution for all possible values of a given sample statistic is called?
(A) Parameter
(B) Random sample
(C) Sampling distribution
(D) Sample space - CORRECT ANSWER (C) Sampling distribution
The sampling distribution of a statistic is the distribution of values of the statistic over all possible samples of size n that could have been selected from the reference population.
If the biostatistician uses sampling and estimation methods to monitor how well regulators are complying with policy, determine possible interventions and/or preventive measures of health problems, and set regulations, what function(s) is he/she addressing?
(A) Assurance
(B) Assurance and policy development
(C) Policy development and assessment
(D) Assessment - CORRECT ANSWER (B) Assurance and policy development
The goal of an ANOVA statistical analysis is to determine whether or not:
(A) The means of two samples are different
(B) The means of more than two samples are different
(C) The means of two or more populations are different
(D) None of the above - CORRECT ANSWER (C) The means of two or more populations are different
One of the simplest experimental design is the completely randomized design in which random samples are selected independently from each of g populations. An analysis of variance is used to test if the g population means are the same, or is at least one mean different from the others.
***see #57 for table**
Based on the following partial ANOVA table:
Source of Variation
SS
df
MS
F
Treatment
100
*
25
6.25
Error
60
*
4
Total
160
19
The numerator and denominator degrees of freedom (shown with * in the above table) are:
(A) 3 and 16
(B) 4 and 15
(C) 16 and 3
(D) 15 and 4 - CORRECT ANSWER (B) 4 and 15
In the ANOVA table, each source of variation when divided by its appropriate degrees of freedom provides an estiamte of the variation in the experiment. The total sums of square (Total SS) involves n squared observations, its degrees of freedom is (n - 1). Also, the sum of squares for the treatments involves k (the number of populations) squared observations, thus its degrees of freedom is (k - 1).
Finally, the sum of squares for error is a direct extension of the pooled estimate and its degrees of freedom is (n - k). We note that the two sources of variation and their respective degrees of freedom are combined to obtain the means squares as MS = SS/df. Therefore MS(treat) = SS(treat) / df(treat) or df(treat) = SS(treat) / MS(treat) = 100/25 = 4. Similarly, df(error) = SS(error) / MS(error) = 60/4 = 15.
When considering a contingency table test with 6 rows and 6 columns, this implies that the number of degrees of freedom for the test must be which of the following:
(A) 25
(B) 6
(C) 12
(D) 36 - CORRECT ANSWER (A) 25
The degree of freedom in a contingency table is given by (r-1)(c-1) where r and c are the number columns and rows. Thus we have (6-1)(6-1) = 25.
When performing a nonparametric Wilcoxon rank-sum test, the first step is to combine the data values in the two samples and assign a rank of '1' to which of the following:
(A) The largest observation
(B) The middle observation
(C) The smallest observation
(D) The most frequently occurring observation - CORRECT ANSWER (C) The smallest observation
The ranking procedure for the Wilcoxon rank-sum test is to first combine the data from the two groups, and order the values from the lowest to the highest.
Reference: Rosner Chaper 9 for more details
Tchebysheff's Theorem states that given only k ≥ 1 and regardless of the shape of a population's frequency distribution, the proportion of observations falling within k standard deviations of the mean is:
(A) At least 1 - (1/k2)
(B) At most 1 - (1/k2)
(C) At least 1 - (1/k)2
(D) At most 1 - (1/k)2 - CORRECT ANSWER (A) At least 1 - (1/k2)
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