CH8 - Are your curves normal? Probability and Why it counts 12:07
Descriptive statistics- describe a data set; but we need to get a better picture about
what the data really look like.
Does the phrase “normal curve”
...
CH8 - Are your curves normal? Probability and Why it counts 12:07
Descriptive statistics- describe a data set; but we need to get a better picture about
what the data really look like.
Does the phrase “normal curve” ring a bell? “Bell-shaped”?
Probability:
● Common sense, past experience, an world knowledge (like weather reports)
factor into probability; it assesses the likelihood of some event happening
○ I.e if you toss your keys to your spouse whats the likelyhood they will
catch it?
● In statistics, the normal (bell-shaped) curve provides us with a similar basis for
understanding the PROBABILITY associated with any possible outcome; i.e. the
odds of you passing the next exam are high… if you study!!
● FOCUS ON THE EXTENT to which we can have CONFIDENCE that a particular
outcome is true
○ Probability gives us the the ability to calculate the odds that the research
outcome we find was (or was not) due to chance
Why probability?
● Imagine we conduct a study to determine how long it takes salesclerks to
approach and help hearing-disabled customers
○ We have a confederate enter who is clearly deaf (she uses sign-language
to talk to a friend) or she enters clearly “hearing-able and talking to her
friend - CONTROL GROUP).
○ Our independent variable is the DEAF GROUP vs. Control group
○ Our dependent is the AMOUNT OF TIME it takes for a clerk to approach
and help the customer- measuring if we will get diff. In clerk approach time
depending on if they are deaf
■ If differences DO emerge between these 2 IV levels, can we
confidently say that the differences are due to deafness? Or might
there be another variable at play (like chance) that BETTER
accounts for any observed differences?
Null Hypothesis
(H0): this implies that the mean scores from the treatment and control groups are
EQUAL (µc = µt) ● Consider the idea of “significance” - or the likelihood that a statistical outcome
DID or DID NOT occur by chance
○ That is, if an outcome DID occur by chance, we conclude that the IV is not
responsible for differences in the DV
■ We call this the null
○ If NOT by chance we accept the ALTERNATIVE HYPOTHESIS
(something other than chance brought about the results: most probabl
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