Hi, as per my protocol I aimed at running ANCOVA analysis but I have since learned that an appropriate method would be linear mixed effects model. The problem is that I had my power analysis and an experiment done with ANCOVA in mind. Now I would like to know what the minimum detectable effect size is for the sample I have. All the options I find are for the trials with two arms but I have four of them as well as three measurement times, and five outcomes. Can anyone recommend a good tool? I think this can be done in R but I don't use it so I would prefer another way.
I've always like MLPowSim ( http://www.bristol.ac.uk/cmm/software/mlpowsim/). You set up what you want, it generates code for MLwiN or R (lme4), you tweak the code if you want, and then it runs the power analysis using simulation so depending on your problem it can take a little while. simr ( https://cran.r-project.org/web/packages/simr/index.html ) is also popular.
Daniel Wright has offered good advice. Depending on the area you work in there may be some specific ways. for example in analytical chemistry it is possibe to find minimum detection limits for analytical procedures. You might google something similar for your own area of research to see if something similar exists there. Best wishes, David Booth
This discussion might be useful.
https://www.theanalysisfactor.com/six-differences-between-repeated-measures-anova-and-linear-mixed-models/
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