I'm analyzing reaction time data from a repeated measures ANOVA with the following design:
Factor 1 (between-group):
GROUP (controls, clinical)
Factor 2 (within-group):
TASK TYPE (social, non-social)
Factor 3 (within-group):
DECISION DIFFICULTY (easy, hard)
ANOVA results indicate a significant 2-way interaction (
DIFFICULTY). No other main effects, 2-way interactions, nor the 3-way interaction are significant (all $p > .4)$.
Since there was no effect of task, I pooled data across the 2 task types. I'm not sure what is the right way to go from here in terms of reporting and interpreting the results. My specific questions are:
Should I always perform follow-up tests with a significant 2-way interaction, or should I just stop there and interpret based on the figures (and without further stats)?
Between- or within-group post-hoc: Should post-hoc tests be restricted to an independent t-test between groups (i.e. comparing "pooled easy" data between groups, and "pooled hard" data between groups)? Can I also perform and report a within-group paired t-test comparing "pooled easy" to "pooled hard" within each group?
Interpretation: If neither independent t-test from (2) is significant, can I still interpret the 2-way interaction based on a significant paired t-test from (2)? (The clinical group's reaction times appear to increase with task difficulty, whereas reaction times don't change with task difficulty in controls.)
In the absence of significant between-group t-tests, can I still report these results based on the 2-way interaction and a within-group t-test as "task difficulty affects reaction times in the clinical group and not the control group"? Thank you. I appreciate any help you can give!