I am conducting analyses related to a quasi-experimental study I have completed. Two age groups (Young, Old) were randomly assigned to three condition (Exp1, Exp2, & Control).

I have completed a 2 (age) x 3 (condition) factorial anova, and I predicted that there would be a significant interaction. However, the interaction is marginally significant (p = 08). I am so frustrated, because I would like to proceed to post-hoc analyses. It is particularly frustrating because if I conduct a 2 (age) x 2 (exp conditions) factorial anova, everything turns out beautiful. Somehow including the control condition messes everything up!

My question is: What should I do?

1) Should I proceed to post-hoc with only a marginally significant effect? Will that raise questions later on?

2) Is there some way that I can structure my analyses so that increase power and push the probability over the .05 threshold?

Feel free to offer suggested reading or example articles, and will do the research to save you time explaining out the details.

Thank you!