![]() However, this power analysis only takes into account your ability to detect the interaction- it doesn't take into account the ability to decompose that interaction using simple main effects or anything like that, which would increase the n significantly. Apparently one of the benefits of using a factorial ANOVA is that you can look at a lot of things without significantly increasing n (I think because you can collapse groups when comparing certain interactions). I've actually been reading as many sources as possible and as far as I can tell, that number is correct for detecting two-way and three-way interactions for a 2x2x2 factorial ANOVA. Thank you!!!!!! Again, I really appreciate any help that people can give me. ![]() Since my proposal is Monday and this is a thesis, not a dissertation, please don't suggest anything fancy (like I go program a model in R or something like that), even if it would be more proper :-). Forgive me if this is a silly question, but I'm presenting on Monday and I know my advisor will ask me why these two numbers are identical! I tried looking through power analysis resources online but I haven't found any resources that are geared to early grad students who haven't formally learned how to do power analyses yet. In order to get a large increase in sample size, I basically I have to enter in up to 100 groups, and even 2 groups gives me 128. I get a critical value of 3.920 and a sample size of 128.Īm I getting the same answers because my df is 1? My advisor basically told me there should be a big difference in the number. For the 3-way interaction, I enter in: effect size. Based on this, G*Power says that the critical F is 3.917, and the total sample size is 128. So for the 2-way interaction, I enter in: effect size. ![]() I'm using G*Power 3.1, assuming a medium effect size (since we have no idea what the effect size is), and going for 80% power with an alpha level of. Two of the factors are experimental manipulation (participants are randomized to one of four groups) and one is a measure given at baseline. What I'm entering in makes sense to me, but I was hoping someone could verify everything for me (thank you in advance!). So I've done a power analysis for both, and I keep getting the same n. I'm doing a 2x2x2 ANOVA, and I'm interested in both 2-way and 3-way interactions. I was hoping someone here could help me out- I'd really appreciate it! I have no idea if I'm doing it correctly and my advisor hasn't given me much guidance. I'm trying to do my first (real) power analysis and I'm running into some issues :-/.
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