Repeated measures or two-way ANOVA ? + sample size estimation

A sample of patients will undergo two treatments. Each patient will receive both treatments.One treatment will on the left side and the other different treatment on the right side. Repeated measurements will be done for each side at several time intervals.

My questions are:

Which analysis is appropriate for that case. Two-way ANOVA with treatment and time being the factors, or simply a repeated measures ANOVA because of the two sides dependency.

If it's the latter test, for sample size calculation, should I use in Gpower the ANOVA: repeated measures,within-between interaction option

If it's the two-way ANOVA, how to calculate the sample size for that? Any software?


TS Contributor
You start pushing just 6 hours after you have posted your question?
It's still talkstats here, not McTalkstats.

As for your problem, you did not state a research objective
or research question.


'cause of time constraints. didn't mean to be pushy, sorry about that.

comparing two types of laser treatments for excessive sweating - hyperhidrosis-between both sides of the same patient. Dependent variable will be the reduction in the affected area.