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

FOCUS ON PROBLEM SOLVING 475
Descriptive Statistics
Dependent Variable: VAR00001
VAR00002
VAR00003
Mean
Std. Deviation
N
1.00
2.00
Total
1.00
2.00
Total
1.00
2.00
Total
1.00
2.00
Total
9.0000
5.0000
7.0000
8.0000
9.0000
8.5000
8.5000
7.0000
7.7500
1.58114
1.73205
2.62467
1.87083
1.73205
1.77951
1.71594
2.66667
2.31414
5
5
10
5
5
10
10
10
20
Dependent Variable: VAR00001
Tests of Between-Subjects Effects
Source
Type III Sum
of Squares
df
Mean
Square
F
Sig.
FIGURE 14.6
Portions of the SPSS
output for the twofactor
ANOVA for the
study in Example 14.2.
Corrected Model
Intercept
VAR00002
VAR00003
VAR00002 * VAR00003
Error
Total
Corrected Total
53.750 a
1201.250
11.250
11.250
31.250
48.000
1303.000
101.750
3
1
1
1
1
16
20
19
17.917
1201.250
11.250
11.250
31.250
3.000
5.972
400.417
3.750
3.750
10.417
.006
.000
.071
.071
.005
FOCUS ON PROBLEM SOLVING
1. Before you begin a two-factor ANOVA, take time to organize and summarize the data.
It is best if you summarize the data in a matrix with rows corresponding to the levels of
one factor and columns corresponding to the levels of the other factor. In each cell of the
matrix, show the number of scores (n), the total and mean for the cell, and the SS within
the cell. Also compute the row totals and column totals that are needed to calculate main
effects.
2. For a two-factor ANOVA, there are three separate F-ratios. These three F-ratios use the
same error term in the denominator (MS within
). On the other hand, these F-ratios have different
numerators and may have different df values associated with each of these numerators.
Therefore, you must be careful when you look up the critical F values in the table.
The two factors and the interaction may have different critical F values.