Psychology 138 Exam 2 Study Guide
The exam will follow the same format as the first exam. Here are examples of questions
similar to those that will be in the closed-notes portion of the exam.
Answers are at the bottom of the page.
What is the Gambler's Fallacy?
What is the distinction between descriptive and inferential statistics?
Define the distribution of sample means.
Under what conditions will the distribution of sample means be normal?
If a population has a mean of μ = 12, what will the mean of the
distribution of sample means be?
Which is bigger, the standard deviation of a population or the standard
deviation of the distribution of sample means drawn from that
population (assuming that n > 1)?
What is another name for the standard deviation of the distribution of
sample means?
What does the Central Limit Theorem tell us?
A hypothesis test is a test of the
a) null hypothesis (H0)
b) alternative hypothesis (H1)
Define the alternative hypothesis?
Suppose that a researcher wishes to know if watching soap operas
regularly makes underage girls more likely to become romantically
involved with older men. When teenage girls have boyfriends, their
boyfriends are on average μ = 0.7 years older than they
are. What is the null hypothesis that will be tested?
Suppose that a researcher believes that being angry alters people's
reaction time. Typically, people can respond to auditory stimuli within
μ = 180ms. What is the null hypothesis that will be tested?
The null hypothesis is false and you rejected it. You’ve made a…
a) Correct decision
b) Type I Error
c) Type II Error
Your research led you to report that Skippy Peanut Butter causes AIDS.
In reality, it doesn’t. You’ve made a…
a) Correct decision
b) Type I Error
c) Type II Error
You hypothesized that a certain variable has an effect. In truth, it
really does have an effect. You retained the null hypothesis. You’ve
made a…
a) Correct decision
b) Type I Error
c) Type II Error
The null hypothesis is false. You retained it. You’ve made a…
a) Correct decision
b) Type I Error
c) Type II Error
The null hypothesis is true. You retained it. You’ve made a…
a) Correct decision
b) Type I Error
c) Type II Error
The null hypothesis is true. You rejected it. You’ve made a…
a) Correct decision
b) Type I Error
c) Type II Error
You report that there is no evidence that testosterone levels increase
aggression. Did you retain the null hypothesis?
a) Yes
b) No
If α is high, am I more likely to make a Type I error?
a) Yes
b) No
If the null hypothesis is true, is it possible to make a Type II error?
a) Yes
b) No
If α is high, am I less likely to make a Type II error?
a) Yes
b) No
In statistics, β is the probability of..
The symbol for the probability of making a Type I error when the null
hypothesis is true is...
The probability of correctly rejecting a null hypothesis that is false
is called...
Increasing sample size will...
a) increase power.
b) decrease power.
Increasing α will...
a) increase power.
b) decrease power.
Provided that you correctly specify the direction of an effect, a
1-tailed hypothesis is more powerful than a 2-tailed hypothesis.
a) True
b) False
Which kind of estimate is more likely to be correct?
a) Point estimate
b) Interval estimate
Define confidence interval
Define margin of error
Conceptually, what does Cohen's d measure?
Answers
What is the Gambler's Fallacy?
It is the incorrect belief that in a sequence of independent
random events (e.g., coin tosses), the probability of 1 event is
changed by the outcomes of the preceding events. More
information
What is the distinction
between descriptive and inferential statistics?
Descriptive statistics summarize
tendencies and
characteristics of data. Inferential statistics use sample statistics
to make
inferences about the populations from which the samples were drawn.
Inferential
statistics are used for hypothesis testing. More information
Define the
distribution of sample means.
The distribution of sample means is the collection
of sample
means for all the possible random samples of a particular size (n) that
can be
obtained from a population. More
information
Under what conditions will the
distribution of sample means be normal?
1. If the original population is normal.
or
2. If the sample size n > 30
If a population has a mean of μ = 12,
what will the mean of the distribution of sample means be?
12
Which is bigger, the standard
deviation of a population or the standard deviation of the distribution
of sample means drawn from that population (assuming that n > 1)?
The standard deviation of the population.
What is another name for the standard
deviation of the distribution of sample means?
The standard error of the mean
What does the Central Limit Theorem tell us?
For any population with mean μ and standard deviation σ, the
distribution of sample means for sample size n will approach a normal
distribution with a mean of μ and a standard deviation of σ / sqrt(n)
as n approaches infinity.
A hypothesis test is a test of the
a) null hypothesis (H0)
b) alternative hypothesis (H1)
What is the alternative hypothesis?
The hypothesis the researcher believes to be true. More information
Suppose that a researcher wishes to
know if watching soap operas regularly makes underage girls more likely
to become romantically involved with older men. When teenage girls have
boyfriends, their boyfriends are on average μ = 0.7 years older
than they are. What is the null hypothesis that will be tested?
Watching soap operas has no effect on teenage girls' choice of
boyfriends. Specifically, teenage girls who watch soap operas regularly
will have boyfriends with an average age of μ <= 0.7 years older
than they are.
Suppose that a researcher believes
that being angry alters people's reaction time. Typically, people can
respond to auditory stimuli within μ = 180ms. What is the null
hypothesis that will be tested?
Anger has no effect on reaction time. Specifically, reaction time while
in a state of anger is μ = 180, the same as when not in a state of
anger.
The null hypothesis is false and you
rejected it. You’ve made a…
a) Correct decision
b) Type I Error
c) Type II Error
Your research led you to report that
Skippy Peanut Butter causes AIDS. In reality, it doesn’t. You’ve made
a…
a) Correct decision
b) Type I Error
c) Type II Error
You hypothesized that a certain
variable has an effect. In truth, it really does have an effect. You
retained the null hypothesis. You’ve made a…
a) Correct decision
b) Type I Error
c) Type II Error
The null hypothesis is false. You
retained it. You’ve made a…
a) Correct decision
b) Type I Error
c) Type II Error
The null hypothesis is true. You
retained it. You’ve made a…
a) Correct decision
b) Type I Error
c) Type II Error
The null hypothesis is true. You
rejected it. You’ve made a…
a) Correct decision
b) Type I Error
c) Type II Error
You report that there is no evidence
that testosterone levels increase aggression. Did you retain the null
hypothesis?
a) Yes
b) No
If α is high, am I more likely to make
a Type I error?
a) Yes
b) No
If the null hypothesis is true, is it
possible to make a Type II error?
a) Yes
b) No
If α is high, am I less likely to make
a Type II error?
a) Yes
b) No
In statistics, β is the probability
of..
making a Type II error when the null hypothesis is false. Note: Both
parts of this answer must be present for full credit (i.e., probability
of Type II error AND the fact that it refers only to the situation in
which the null hypothesis is false.).
The symbol for the probability of
making a Type I error when the null hypothesis is true is...
α
The probability of correctly rejecting
a null hypothesis that is false is called...
Statistical power (Note: just "power" is also acceptable)
Increasing sample size will...
a) increase power.
b) decrease power.
Increasing
α will...
a) increase power.
b) decrease power.
Provided that you correctly specify
the direction of an effect, a 1-tailed hypothesis is more powerful than
a 2-tailed hypothesis.
a) True
b) False
Which kind of estimate is more likely
to be correct?
a) Point estimate
b) Interval estimate
Define confidence interval
An interval estimate that is calculated to contain the
population parameter a certain percentage of the time. More
information
Define margin of error
The distance from the point estimate to the upper bound (or lower
bound) of a confidence interval. More information
Conceptually, what does Cohen's d measure?
The distance between two means in standard deviation units. More
information