# PSY 520 Grand Canyon University Ch 13 14 & 15 Null Hypothesis Statistics Exercises

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psy 520

Grand Canyon University

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PSY520

Topic 5 exercises

Complete the following exercises located at the end of each chapter and put them into a Word document to be submitted as directed by the instructor.

Show all relevant work; use the equation editor in Microsoft Word when necessary.

1.Chapter 13, numbers 13.6, 13.8, 13.9, and 13.10

2.Chapter 14, numbers 14.11, 14.12, and 14.14

3.Chapter 15, numbers 15.7, 15.8, 15.10 and 15.14

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Here you go!This was a lot more work than I thought it would be 😧

Topic 5 Exercises
Chapter 13
13.6

It’s well established, we’ll assume, that lab rats require an average of 32 trials in a complex
water maze before reaching a learning criterion of three consecutive error-less trials. To
determine whether a mildly adverse stimulus has any effect on per-formance, a sample of
seven lab rats were given a mild electrical shock just before each trial.
(a) Given that X = 34.89 and s = 3.02, test the null hypothesis with t, using the .05 level of
significance.
Null hypothesis
H0: µ = 32 trials
Alternative hypothesis:
HA: µ ≠ 32 trials
A two-tailed, one sample t-test for the population mean was performed, and yielded the
following test statistic and p-value:
t(df = 6) = 2.53
p = 0.0446
At a significance level of 0.05, the null hypothesis should be rejected (p < ⍺).
Therefore, there is sufficient evidence to conclude that the true number of trials required to learn
the water maze is a value other than 32.
(b) Construct a 95 percent confidence interval for the true number of trials required to
learn the water maze.
Sample Mean ± Margin of Error
34.89 ± 2.447*(1.14)
(32.097, 37.683)
(c) Interpret this confidence interval.
We are 95% confident that the true population number of trials required to learn the water maze
falls between 32.1 and 37.7.

13.8

Assume that, on average, healthy young adults dream 90 minutes each night, as inferred
from a number of measures, including rapid eye movement (REM) sleep. An investigator
wishes to determine whether drinking coffee just before going to sleep affects the amount of
dream time. After drinking a standard amount of coffee, dream time is monitored for each
of 28 healthy young adults in a random sample. Results show a sample mean, X, of 88

minutes and a sample standard deviation, s, of 9 minutes.
(a) Use t to test the null hypothesis at the .05 level of significance
Null hypothesis
H0: µ = 90 minutes of dreaming a night
Alternative hypothesis:
HA: µ ≠ 90 minutes of dreaming a night
A two-tailed, one sample t-test for the population mean was performed, and yielded the
following test statistic and p-value:
t(df=27) = -1.18
p = 0.2499
At a significance level of 0.05, the null hypothesis should not be rejected (p > ⍺).
Therefore, there is not sufficient evidence to conclude that the true length of time that a healthy,
young adult dreams each night is any value other than 90 minutes.
(b) If appropriate (because the null hypothesis has been rejected), construct a 95 percent
confidence interval and interpret this interval.
As the decision that was made was to fail to reject the null hypothesis, there is no need to
construct a confidence interval. If an interval were constructed, it would contain the null
hypothesis value of 90 minutes.

13.9

In the gas mileage test described in this chapter, would you prefer a smaller or a larger
sample size if you were:
(a) the car manufacturer? Why?
A smaller sample size would be preferable.
As the sample size decreases, the width of the confidence interval increases, which is ideal for
the car manufacturer.
(b) a vigorous prosecutor for the federal regulatory agency? Why?
A larger sample size would be preferable.
As the sample size increases, the width of the confidence interval decreases, which makes the
estimate more precise. This is beneficial for the federal agency because more prosecutions would
occur.

13.10 Even though the population standard deviation is unknown, an investigator uses z rather
than the more appropriate t to test a hypothesis at the .05 level of significance.

(a) Is the true level of significance larger or smaller than .05?
Larger.
(b) Is the true critical value larger or smaller than that for the critical z?
Larger.

Chapter 14
14.11 To test compliance with authority, a classical experiment in social psychology requires
subjects to administer increasingly painful electric shocks to seemingly helpless victims
who agonize in an adjacent room. Each subject earns a score between 0 and 30, depending
on the point at which the subject refuses to comply with authority—an investigator,
dressed in a white lab coat, who orders the administration of increasingly intense shocks. A
score of 0 signifies the subject’s unwillingness to comply at the very outset, and a score of
30 signifies the subject’s willingness to comply completely with the experimenter’s orders.
Ignore the ...

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