A Step by Step Guide for SPSS and Exercise Studies

84 Statistical tests
Figure 25
instructions may help these participants to perform better. Figure 26 shows
that there is no evident relationship between the residuals and the order in
which the dependent measure was taken.
If some of these assumptions are violated, you may have to transform the
dependent variable. However, bear in mind that the F value is relatively robust
to such violations, provided that the sample sizes in the groups of the
independent variables are relatively equal.
How to carry out the test
Suppose you want to look at differences in self-reported effort (dependent
variable) in a physical education class. Factorial ANOVA will examine
differences in effort among different levels (1 ˆ little, 2 ˆ moderate, 3 ˆ high) of
enjoyment of physical education and support that pupils receive from their PE
teachers. Note that you need to have two variables in the data file which contain
the codes for the different levels (Figure 27). Variable coding is essential to
carry out the factorial ANOVA test (see Compute in the Transform menu to
create a new categorical variable with the codes for the different groups).
The effects of enjoyment and support are called main effects. Factorial
ANOVA will also test for interaction effects, that is, whether there is a combined