1
MATH 1280 Milestone 3_Introduction to Statistics
(2020) – University of the People
Tracie spins the four-colored spinner shown below. She records the total number of
times the spinner lands on the color red and con
...
1
MATH 1280 Milestone 3_Introduction to Statistics
(2020) – University of the People
Tracie spins the four-colored spinner shown below. She records the total number of
times the spinner lands on the color red and constructs a graph to visualize her results.
Which of the following statements is TRUE?
•
If Tracie spins the spinner 1,000 times, it would land on red close to 250
times.
•
If Tracie spins the spinner 1,000 times, the relative frequency of it landing on red will
remain constant.
•
If Tracie spins the spinner 4 times, it will land on red at least once.
•
The theoretical probability of the spinner landing on red will change with every spin
completed.RATIONALE
If we make the assumption that the area of the colors represents the true proportion,
then each color is equally weighted. Since there are four colors we would expect them to
come up roughly 1/4 of the time. So on 1000 rolls the expected value = n*p = 1000*0.25
= 250.
CONCEPT
Law of Large Numbers/Law of Averages
2
Two sets A and B are shown in the Venn diagram below.
Which statement is TRUE?
•
There are a total of 17 elements shown in the Venn diagram.
•
Set A has 12 elements.
•
Set B has 5 elements.
•Sets A and B have 15 common elements.
RATIONALE
The number of elements of Set A is everything in Circle A, or 10+2 = 12 elements.
The number of elements of Set B is everything in Circle B, or 5+2 = 7 elements, not 5
elements.
The intersection, or middle section, would show the common elements, which is 2
elements, not 15 elements.
To get the total number of items in the Venn diagram, we add up what is in A and B and
outside, which is 10+2+5+3 = 20 elements, not 17 elements.
CONCEPT
Venn Diagrams
3
Using the Venn Diagram below, what is the conditional
probability of event B occurring, assuming event A has happened [P(B|A)]?
•
0.41
•0.63
•
0.24
•
0.77
RATIONALE
To get the probability of B given A has occurred, we can use the following conditional
formula:
The probability of A and B is the intersection, or overlap, of the Venn diagram, which is
0.41.
The probability of A is all of Circle A, or 0.24 + 0.41 = 0.65.
CONCEPT
Conditional Probability
4
The gender and age of Acme Painting Company's employees are shown below.
Age Gender
23 Female
23 Male
24 Female
26 Female
27 Male
28 Male
30 Male31 Female
33 Male
33 Female
33 Female
34 Male
36 Male
37 Male
38 Female
40 Female
42 Male
44 Female
If the CEO is selecting one employee at random, what is the chance he will
select a male OR someone in their 40s?
•
1/3
•
1/2
•
11/18
•
1/18
RATIONALE
Since it is possible for an employee to be a male and a person in their 40s, these two
events are overlapping. We can use the following formula:Of the 18 employees, there are 9 females and 9 males, so . There are a total of 3
people in their 40s, so . Of the people in their 40s, only one is male so .
CONCEPT
"Either/Or" Probability for Overlapping Events
5
Which of the following is a condition of binomial probability distributions?
•
All observations are mutually exclusive.
•
All observations are made randomly.
•
All observations made are dependent on each other.
•
All observations made are independent of each other.
RATIONALE
In the binomial distribution we always assume independence of trials. This is why we
simply multiply the probability of successes and failures directly to find the overall
probability.
CONCEPT
Binomial Distribution
6
La'Vonn rolled a die 100 times. His results are below.
Number Times Rolled
1 182 20
3 15
4 17
5 14
6 16
What is the relative frequency for La'Vonn rolling a 3? Answer choices are
rounded to the hundredths place.
•
0.01
•
0.15
•
0.07
•
0.38
RATIONALE
The relative frequency of a 3 is:
CONCEPT
Relative Frequency Probability/Empirical Method
7
For a math assignment, Jane has to roll a set of six standard dice and record the results
of each trial. She wonders how many different outcomes are possible after rolling all six
dice.
What is the total number of possible outcomes for each trial?
•
216•
46,656
•
7,776
•
36
RATIONALE
We can use the general counting principle and note that for each step, we simply
multiply all the possibilities at each step to get the total number of outcomes. Each die
has 6 possible outcomes, so the overall number of outcomes for rolling 6 die with 6
possible outcomes each is:
CONCEPT
Fundamental Counting Principle
8
Zhi and her friends moved on to the card tables at the casino. Zhi wanted to figure out
the probability of drawing a face card or an Ace.
Choose the correct probability of drawing a face card or an Ace. Answer
choices are in the form of a percentage, rounded to the nearest whole
number.
•
31%
•
8%
•
25%
•
4%
RATIONALESince the two events, drawing a face card and drawing an ace card, are non-overlapping,
we can use the following formula:
CONCEPT
"Either/Or" Probability for Non-Overlapping Events
9
Colleen has 6 eggs, one of which is hard-boiled while the rest are raw. Colleen can't
remember which of the eggs are raw.
Which of the following statements is true?
•
The probability of Colleen selecting the hard-boiled egg on her first try is 1/5.
•
If Colleen selected one egg, cracked it open and found out it was raw, the
probability of selecting the hard-boiled egg on her second pick is 1/5.
•
If Colleen selected one egg, cracked it open and found out it was raw, the probability of
selecting the hard-boiled egg on her second pick is 1/6.
•
The probability of Colleen selecting a raw egg on her first try is 1/6.
RATIONALE
The probability of choosing the hard-boiled egg is 1/6. If she cracks an egg and it is not
the hard-boiled egg, then it becomes 1/5 on the next try because there are now only 5
eggs remaining and one has to be the hard-boiled egg as she did not pick it on the first
try.
CONCEPT
Independent vs. Dependent Events
10
Eric is randomly drawing cards from a deck of 52. He first draws a red card, places it
back in the deck, shuffles the deck, and then draws another card.What is the probability of drawing a red card, placing it back in the deck,
and drawing another red card? Answer choices are in the form of a
percentage, rounded to the nearest whole number.
•
4%
•
22%
•
25%
•
13%
RATIONALE
Since Eric puts the card back and re-shuffles, the two events (first draw and second
draw) are independent of each other. To find the probability of red on the first draw and
second draw, we can use the following formula:
Note that the probability of drawing a red card is or for each event.
CONCEPT
"And" Probability for Independent Events
11
A basketball player makes 60% of his free throws. We set him on the free throw line and
asked him to shoot free throws until he misses. Let the random variable X be the
number of free throws taken by the player until he misses.
Assuming that his shots are independent, find the probability that he will
miss the shot on his 6th throw.
•
0.03110
•
0.00614•
0.04666
•
0.01866
RATIONALE
Since we are looking for the probability until the first success, we will use the following
Geometric distribution formula:
The variable k is the number of trials until the first success, which in this case, is 6
throws.
The variable p is the probability of success, which in this case, a success is considered
missing a free throw. If the basketball player has a 60% of making it, he has a 40%, or
0.40, chance of missing.
CONCEPT
Geometric Distribution
12
Three hundred students in a school were asked to select their favorite fruit from a choice
of apples, oranges, and mangoes. This table lists the results.
Boys Girls
Apple 66 46
Orange 52 41
Mango 40 55
If a survey is selected at random, what is the probability that the student is a
girl who chose apple as her favorite fruit? Answer choices are rounded to
the hundredths place.
•0.37
•
0.41
•
0.15
•
0.59
RATIONALE
If we want the probability that the survey is from a girl and also chose apple as her
favorite, we just need to look at the box that is associated with both categories, or 46. To
calculate the probability, we can use the following formula:
CONCEPT
Two-Way Tables/Contingency Tables
13
Which of the following situations describes a continuous distribution?
•
A probability distribution showing the amount of births in a hospital in a month
•
A probability distribution showing the average number of days mothers spent in the
hospital
•
A probability distribution showing the weights of newborns
•
A probability distribution showing the number of vaccines given to babies during their
first year of life
RATIONALE
Since the weight of newborns can be an infinite number of values, such as 8 pounds, 9
ounces, etc, this would be an example of a continuous distribution.
CONCEPTProbability Distribution
14
A credit card company surveys 125 of its customers to ask about satisfaction with
customer service. The results of the survey, divided by gender, are shown below.
Males Females
Extremely Satisfied 25 7
Satisfied 21 13
Neutral 13 16
Dissatisfied 9 14
Extremely Dissatisfied 2 5
If you were to choose a female from the group, what is the probability that
she is satisfied with the company's customer service? Answer choices are
rounded to the hundredths place.
•
0.13
•
0.62
•
0.38
•
0.24
RATIONALE
The probability of a person being "satisfied" given she is a female is a conditional
probability. We can use the following formula:Remember, to find the total number of females, we need to add all values in this
column: 7 + 13 + 16 + 14 + 5 = 55.
CONCEPT
Conditional Probability and Contingency Tables
15
Annika was having fun playing poker. She needed the next two cards dealt to be
diamonds so she could make a flush (five cards of the same suit). There are 15 cards left
in the deck, and five are diamonds.
What is the probability that the two cards dealt to Annika (without
replacement) will both be diamonds? Answer choices are in percentage
format, rounded to the nearest whole number.
•
13%
•
10%
•
33%
•
29%
RATIONALE
If there are 15 cards left in the deck with 5 diamonds, the probability of being dealt 2
diamonds if they are dealt without replacement means that we have dependent events
because the outcome of the first card will affect the probability of the second card. We
can use the following formula:
The probability that the first card is a diamond would be 5 out of 15, or . The
probability that the second card is a diamond, given that the first card was also a
diamond, would be because we now have only 14 cards remaining and only 4 ofthose cards are diamond (since the first card was a diamond).
So we can use these probabilities to find the probability that the two cards will both be
diamonds:
CONCEPT
"And" Probability for Dependent Events
16
David is playing a game where he flips two coins and counts the total number of
heads. The possible outcomes and probabilities are shown in the probability
distribution below.
What is the expected value for the number of heads from flipping two coins?
•
1
•
3
•
1.5
•
2
RATIONALEThe expected value, also called the mean of a probability distribution, is found by adding
the products of each individual outcome and its probability. We can use the following
formula to calculate the expected value, E(X):
CONCEPT
Expected Value
17
Luke went to a blackjack table at the casino. At the table, the dealer has just shuffled a
standard deck of 52 cards.
Luke has had good luck at blackjack in the past, and he actually got three blackjacks
with Queens in a row the last time he played. Because of this lucky run, Luke thinks that
Queens are the luckiest card.
The dealer deals the first card to him. In a split second, he can see that it is a face card,
but he is unsure if it is a Queen.
What is the probability of the card being a Queen, given that it is a face
card? Answer choices are in a percentage format, rounded to the nearest
whole number.
•
4%
•
77%
•
33%
•
8%
RATIONALE
The probability of it being a Queen given it is a Face card uses the conditional formula:Note that there are 12 out of 52 that are face cards. Of those 12 cards, only 4 of them are
also Queens.
CONCEPT
Conditional Probability
18
Select the following statement that describes non-overlapping events.
•
Jon needs to roll an even number to win. When it’s his turn, he rolls a two.
•
To win, Jon needs a red card. He receives a Queen of Diamonds.
•
Jon wants a face card so he can have a winning hand, and he receives the
eight of clubs.
•
Receiving the King of Hearts fulfills Jon's need of getting both a face card and a heart.
RATIONALE
Events are non-overlapping if the two events cannot both occur in a single trial of a
chance experiment. Since he wants a face card {Jack, Queen or King} and he got an
eight {8}, there is no overlap.
CONCEPT
Overlapping Events
19
Tim rolls two six-sided dice and flips a coin.
All of the following are possible outcomes, EXCEPT:
•
1, Tails, 6
•
Heads, 3, 4
•
2, 8, Heads•
5, 2, Tails
RATIONALE
Recall that a standard coin has two values, {Heads or Tails}, while a standard die has six
values {1, 2, 3, 4, 5, or 6}. So, obtaining a 2 is possible, however the 8 is not.
CONCEPT
Outcomes and Events
20
The average number of babies born at a private hospital's maternity wing is 6 per hour.
What is the probability that three babies are born during a particular 1-
hour period in this maternity wing?
•
0.16
•
0.13
•
0.09
•
0.20
RATIONALE
Since we are finding the probability of a given number of events happening in a fixed
interval when the events occur independently and the average rate of occurrence is
known, we can use the following Poisson distribution formula:
The variable k is the given number of occurrences, which in this case, is 3 babies.
The variable λ is the average rate of event occurrences, which in this case, is 6 babies.
CONCEPT
Poisson Distribution21
Mark looked at the statistics for his favorite baseball player, Jose Bautista. Mark looked
at seasons when Bautista played 100 or more games and found that Bautista's
probability of hitting a home run in a game is 0.173.
If Mark uses the normal approximation of the binomial distribution, what
will be the variance of the number of home runs Bautista is projected to hit
in 100 games? Answer choices are rounded to the tenths place.
•
14.3
•
17.3
•
3.8
•
0.8
RATIONALE
In this situation, we know:
n = sample size = 100
p = success probability = 0.173
We can also say that q, or the complement of p, equals:
q = 1 - p = 1 - 0.173 = 0.827
The variance is equivalent to n*p*q:
CONCEPT
Normal Distribution Approximation of the Binomial Distribution
22Using this Venn diagram, what is the probability that event A or event B
occurs?
•
0.60
•
0.78
•
0.42
•
0.22
RATIONALE
To find the probability that event A or event B occurs, we can use the following formula
for overlapping events:
The probability of event A is ALL of circle A, or 0.39 + 0.18 = 0.57.
The probability of event B is ALL of circle B, or 0.21 + 0.18 = 0.39.
The probability of event A and B is the intersection of the Venn diagram, or 0.18.
We can also simply add up all the parts = 0.39 + 0.18 + 0.21 = 0.78.CONCEPT
"Either/Or" Probability for Overlapping Events
23
Peter randomly draws a card from a deck of 24. The odds in favor of his drawing a spade
from the cards are 1:3.
What is the probability ratio for Peter to draw a spade?
• •• •
RATIONALE
Recall that we can go from " " odds to a probability by rewriting it as the fraction "
". So odds of 1:3 is equivalent to the following probability:
CONCEPT
Odds
24
What is the probability of NOT rolling a four when rolling a six sided die?
• • •RATIONALE
Recall that the probability of a complement, or the probability of something NOT
happening, can be calculated by finding the probability of that event happening, and
then subtracting from 1. Note that the probability of rolling a four would be 1/6. So the
probability of NOT rolling a four is equivalent to:
CONCEPT
Complement of an Event
25
A magician asks an audience member to pick any number from 6 to 15.What is the theoretical probability that an individual chooses the number
the magician has in mind?
• • • •RATIONALE
If we suppose that the card chosen by the magician is fixed, then there are 10 possible
values, {6, 7, 8, 9, 10, 11, 12, 13, 14, or 15}, that are all equally likely. So, the probability
that a specific value is chosen is:
CONCEPT
Theoretical Probability/A Priori Method
26
Which of the following is an example of a false negative?
•Test results confirm that a woman is not pregnant.
•
Test results indicate that a woman is not pregnant when she is.
•
Test results confirm that a woman is pregnant.
•
Test results indicate that a woman is pregnant when she is not.
RATIONALE
Since the test results indicate negatively, showing that the woman is not pregnant when
in fact she is pregnant, this is a false negative.
CONCEPT
False Positives/False Negatives
27
Kendra was trying to decide which type of frozen yogurt to restock based on popularity:
flavors with chocolate or flavors without chocolate. After studying the data, she noticed
that chocolate flavors sold best on the weekdays and on the weekends, but not best
overall.
Which paradox has Kendra encountered?
•
False Negative
•
Simpson's Paradox
•
Benford's Law
•
False Positive
RATIONALE
This is an example of Simpson's paradox, which is when the trend overall is not the
same that is examined in smaller groups. Since the sale of chocolate flavors is larger onthe weekends, but this trend changes when looking at sales overall, this is a reversal of
the trend.
CONCEPT
Paradoxes
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