Related to an earlier question on power analysis for multiple regression, a social science researcher asked me about power analysis for moderator regression (i.e., an interaction effect). The researcher asked me:
I seem to recall that power of tests for moderation with two continuous predictor variables is low - do you know the minimum sample size requirement in this context?
From the context, it can further be assumed that this is an observational study (not an experimental study) and that the dependent variable is continuous.
- What advice would you give regarding calculating the minimum sample size required?
- Are there any caveats that you would present?