I have conducted a repeated measures ANOVA, with 2 factors:
- One between factor (
Ex_control
: exercise intervention versus control) - One within factor (
time
: pre/post intervention).
Questions
- Should I first refer to the table labelled
within-subject effect
and specifically the box labelledtime*Ex_control
? - Does this table show whether or not there was a significant between or within group change as a result of the intervention?
Best Answer
The line labelled
time*Ex_control
will tell you whether there is a statistically significanttime
bygroup
interaction.In the case of pre-post treatment-control design, this is often the effect of greatest interest. It is relevant to assessing whether the effect of time varies between groups. For example, if it is statistically significant you would then look at the direction of the sample means to see whether for example the group that received the exercise group improved more over time than the control group.
This can be contrasted with the two main effects. The main effect of time will test whether there is a significant change over time averaged across both groups. The main effect of group will test whether on average one group scored higher on the dependent variable than the other.