A Step by Step Guide for SPSS and Exercise Studies

Statistical tests 91
Figure 28
The Residual plot shows that the residuals are not random. As you can see at
the top centre of the plot, there is a pattern of decreased variability between
observed and predicted residuals as the values increase (Figure 29). Taken
together, Figures 28 and 29 indicate that the homogeneity assumption is not
satisfied. One way of dealing with this problem is to transform the dependent
variable in order to achieve homogeneity. Alternatively, you can go back and
create different groups of almost equal size. ANOVA tests are not affected too
much by violations of the homogeneity assumption as long as the group sizes are
almost equal.
The eta squared value for enjoyment ( 2 ) shows that this variable explains
around 36% of the variance in effort scores. The power of the two main effects is
large, whereas the power of the interaction effect is very small. The F values for
support and enjoyment are significant. The interaction effect of support and
enjoyment has a non-significant F value. Therefore, there are two significant
main effects but no significant interaction effect (Table 27).
An inspection of the mean scores shows that as the levels of enjoyment and
support increase, so does the level of effort in PE classes (Tables 28 and 29).
The ANOVA tests showed that the three enjoyment and support groups differ
in effort. However, you need to find out which group differs from the others.
Note that if one of the main effects was not significant (e.g., enjoyment), you
should have stopped here and reported that the three enjoyment groups did not