Interaction analyses — Power (part 1)

[This was first posted on my blog]

Edit 5/24/21: I’ve turned the code underlying these posts into an R package: https://dbaranger.github.io/InteractionPoweR. I’d recommend using this package for your own power analyses, rather than the original posted code, as it’s a lot easier to use, has more features, and I’ve fixed some minor errors.

I conduct interaction (aka ‘moderation’) analyses a lot. As a result, I was interested to read commentaries online about interaction analyses, and the question of how large of a sample is required [1,2]…