Statistical Methods for Psychology

Using 1, 2,... , 6 deliberately ignores this
relationship. Apparently the human body responds
in a nonlinear way to the increase in actual dose
levels.
12.27 Effect sizes for Exercise 12.1

c 1 5 10.667 c 2526 c 3521 c 4524

MSerror 5 5.60 4.51 2 2.54

2 0.42 2 1.69

12.29The contrast between the Positive and Negative
mood conditions was significant (t(27) 5 3.045, p,.05).
This leads to an effect size of d5 c/ 5

. The two groups dif-
fer by over 1 1 3 standard deviations. It is evident that
inducing a negative mood leads to more checking behav-
ior than introducing a positive mood. (If we had com-
pared the Positive and No mood conditions, the
difference would not have been significant. However, I
had not planned to make that comparison.

12.31 This requires students to make up their own example.

Chapter 13

13.1 Source df SS MSN F

Parity 1 13.067 13.067 3.354

Size Age 2 97.733 48.867 12.541*

P 3 S 2 17.733 8.867 2.276

Error 54 210.400 3.896

Total 59 338.933

*p,.05 [F.05(2,54) 5 3.17]

13.3 The mean for these primiparous mothers is not expected
to be a good estimate of the mean for the population of
all primiparous mothers because the sample is not rep-
resentative of the population. For example, 50% of the
population of primiparous mothers would not be
expected to give birth to LBW infants.

13.5 Exercise 11.3 as a factorial

Source df SS MS F

Delay 2 188.578 94.289 3.22

Area 2 356.044 178.022 6.07*

D 3 A 4 371.956 92.989 3.17*

Error 36 1055.200 29.311

Total 44 1971.778

*[F.05(2,36) 5 3.27; F.05(4,36) 5 2.64]

13.7 In Exercise 13.5, if A refers to Area:

the treatment effect for the Neutral site 5

13.9 Group Nvs. Group A: t 5 3.03. Group Nvs. Group Bt 5
3.00. With two ttests, each on 36 df(for MSerror) with
a5.05 2 5 .025 (two-tailed), the critical value is
6 2.339. We would reject H 0 in each case.

>

24.222 2 28.2=3.978

aN 1 = X.1 2 X..

p 6 0.5

>

>

5.6> 1 16.907=5.6>4.11=1.36

1 MSerror

d 3 = d 4 =

d 1 = d 2 =

13.11Source df SS MS F

Age 1 115.60 115.60 17.44*

Level 1 792.10 792.10 119.51*

Age 3 Level 1 152.10 152.10 22.95*

Error 36 238.60 6.6278

Total 39 1298.40

*p,.05 [F.05 (1,36) 5 4.12]

13.13 Made-up data with main effects but no interaction:

Cell means: 8 12

46

13.15 The interaction was of primary interest in an experiment

by Nisbett in which he showed that obese people varied

the amount of food they consumed depending on

whether a lot or a little food was visible, while normal

weight subjects ate approximately the same amount un-

der the two conditions.

13.17Source df SS MS F

Age 1 11.704 11.704 20.02*

Daycare 1 2.639 2.639 4.51*

A 3 D 1 0.038 0.038 , 1

Error 36 21.050 0.585

Total 39

*

13.19

13.21Magnitude of effect for avoidance learning data in

Exercise 13.5:

hD^2 =

SSdelay

SStotal

=

188.578

1971.778

=.10

=

17.733 21121221 3.896 2

338.933 1 3.896

=.03

vPS^2 =

SSPS 21 p 2121 s 212 MSerror

SStotal 1 MSerror

=

97.733 21221 3.896 2

338.933 1 3.896

=.26

vS^2 =

SSsize 21 S 212 MSerror

SStotal 1 MSerror

=

13.067 21121 3.896 2

338.933 1 3.896

=.03

vP^2 =

SSparity 21 p 212 MSerror

SStotal 1 MSerror

hPS^2 =

SSPS

SStotal

=

17.733

338.933

=.05

hS^2 =

SSsize

SStotal

=

97.733

338.933

=.29

hP^2 =

SSparity

SStotal

=

13.067

338.933

=.04

p 6 .05 3 F.05,(1,36)=4.11 4

746 Answers