I have been struggling quite a lot with finding a way to conduct a power analysis for a hierarchical regression with a three-way interaction. I will put 2 control variables in Step 1, 3 IVs in Step 2 for main effects, and the three-way interaction in Step 3. I expect an effect size of 0.15, Power = 0.8, and alpha = 0.05. Could anyone please help me how I can perform a power analysis for the above regression using G*Power analysis? Moroever, in case I need to use the power analysis that is used for ANCOVA (since it is basically a regression too), how do I calculate the dfs of my model? Help is much appreciated.