Statistics for the Behavioral Sciences by Frederick J. Gravetter, Larry B. Wallnau ISBN 10: 1305504917 ISBN 13: 9781305504912

678 APPENDIX C | Solutions for Odd-Numbered Problems in the Text
Source SS df MS
Between Treatments 32 5
Use 24 1 24 F(1, 18) = 14.4
School level 4 2 2 F(2, 18) = 1.2
Interaction 4 2 2 F(2, 48) = 1.2
Within Treatments 30 18 1.67
Total 62 23
For df = 1, 18 the critical value is 4.41 and for
df = 2, 18 it is 3.55. The main effect for Facebook
use is significant. For df = 2, 18 the critical value is
3.55. The other main effect and the interaction are
not significant.
b. Grades are significantly lower for Facebook
users. A difference exists for all three grade levels
but appears to increase as the students get older
although there is no significant interaction.
25. a.
Source SS df MS
Between Treatments 270 3
Self-Esteem 150 1 150 F(1, 20) = 34.88
Audience 96 1 96 F(1, 20) = 22.33
Interaction 24 1 24 F(1, 20) = 5.58
Within Treatments 86 20 4.3
Total 356 23
With df = 1, 20 the critical value is 4.35 for all three
tests. Both main effects and the interaction are significant.
Overall, there are fewer errors for the high selfesteem
participants and for those working alone. The
audience condition has very little effect on the high
self-esteem participants but a very large effect on those
with low self-esteem.
b. For the self-esteem main effect, η 2 = 150
236 = 0.636,
for the audience main effect, η 2 = 96
182 = 0.527, and
for the interaction, η 2 = 24
110 = 0.218.
CHAPTER 15
Correlation
1. A positive correlation indicates that X and Y change in
the same direction: As X increases, Y also increases.
A negative correlation indicates that X and Y tend
to change in opposite directions: As X increases, Y
decreases.
3. SP = 9
5. a. The scatter plot shows points widely scattered
around a line sloping down to the right.
b. The correlation is small and negative; around −0.4
to −0.6.
c. For these scores, SS X
= 18, SS Y
= 8, and
SP = −7. The correlation is r = 2 7
12 = −0.583.
7. a. The scatter plot shows four points forming a
square. There is no linear trend so the correlation
is near zero.
b. SS X
= 9, SS Y
= 25, and SP = 0. The correlation is
r = 0
15 = 0.
9. a. The scatter plot shows points scattered around a
line sloping up to the right. The correlation should
be 0.4 to 0.6.
b. SS X
= 6, SS Y
= 24, and SP = 5. The correlation is
r = 5
12 = 0.42.
11. a. For the children, SS = 32 and for the birth
parents, SS = 14. SP = 15. The correlation is
r = 0.709.
b. For the children, SS = 32 and for the adoptive
parents SS = 16. SP = 3. The correlation is
r = 0.133.
c. The children’s behavior is strongly related to their
birth parents and only weakly related to their
adoptive parents. The data suggest that the behavior
is inherited rather than learned.
13. a. For the men’s weights, SS = 18 and for their
incomes, SS = 11,076. SP = 330. The correlation
is r = 0.739.
b. With n = 8, df = 6 and the critical value is 0.707.
The correlation is significant.
15. a. r = 0.811
b. r = 0.576
c. r = 0.404
17. a. r XY−Z
= 0.32
0.655 = 0.489
b. r XZ−Y
= 2 0.02
0.571 = −0.035
19. a. r S
= +0.907
b. With n = 11, the critical value is 0.618. The correlation
is significant.
21. a. r S
= 0.732 using the special formula or
r S
= 0.727 using the Pearson formula on
the ranks.
b. For n = 8, the critical value is 0.738 for
α = .05. The correlation is not significant.
23. a. Using the pain ratings as the X variable and coding
money as 1 and plain paper as 0 for the Y variable
produces SS X
= 144.44, SS Y
= 4.5, and SP = −17.
The point-biserial correlation is r = −0.667.
b. r 2 = 0.445
c. The formula produces r 2 = 0.443.