Statistical Methods for Psychology

Exercises 171

6.21 Suppose we asked a group participants whether they liked Monday Night Football, made
them watch a game, and then asked them again. Our interest lies in whether watching a game
changes people’s opinions. Out of 80 participants, 20 changed their opinion from Favorable
to Unfavorable, while 5 changed from Unfavorable to Favorable. (The others did not change).
Did watching the game have a systematic effect on opinion change? (This test on changes is
a test suggested by McNemar [1969] and is often referred to as the McNemar test.)
a. Run the test.
b. Explain how this tests the null hypothesis that you wanted to test.
c. In this situation the test does not answer our question of whether watching football has
a serious effect on opinion change. Why not?

6.22 Pugh (1983) conducted a study of how jurors make decisions in rape cases. He presented
358 people with a mock rape trial. In about half of those trials the victim was presented as
being partly at fault, and in the other half of the trials she was presented as not at fault. The
verdicts are shown in the following table. What conclusion would you draw?
Fault Guilty Not Guilty Total
Little 153 24 177
Much 105 76 181
Total 258 100 358

6.23 The following SPSS output represents that analysis of the data in Exercise 6.17.

a. Verify the answer to Exercise 6.17a.

b. Interpret the row and column percentages.

c. What are the values labeled “Asymp. Sig.”?

d. Interpret the coefficients.

RACE*GOAL Crosstabulation

Goal

Gain Lose Maintain Total

RACE African-Amer Count 24 47 28 99

Expected Count 8.6 62.3 28.1 99.0

% within RACE 24.2% 47.5% 28.3% 100.0%

% within GOAL 43.6% 11.8% 15.6% 15.6%

% of Total 3.8% 7.4% 4.4% 15.6%

White Count 31 352 152 535

Expected Count 46.4 336.7 151.9 535.0

% within RACE 5.8% 65.8% 28.4% 100.0%

% within GOAL 56.4% 88.2% 84.4% 84.4%

% of Total 4.9% 55.5% 24.0% 84.4%

Total Count 55 399 180 634

Expected Count 55.0 399.0 180.0 634.0

% within RACE 8.7% 62.9% 28.4% 100.0%

% within GOAL 100.0% 100.0% 100.0% 100.0%

% of Total 8.7% 62.9% 28.4% 100.0%

Exhibit 6.2

(continues)