Hello,  I am looking for a sample size function for samples sizes, to test proportions that are not binomial proportions.  The proportions represent a ratio of (final measure) / (baseline measure) on the same experimental unit.  Searches using RSeek and such bring multiple hits for binomial proportions, but that doesn't seem to fit my situation.  Perhaps there's some standard terminology from a different field that would provide better hits than deeming this a 'rate' or a 'proportion'.

Of course, most sample size functions assume a normal distribution, while this data will be bounded between 0 and 1.  The scientist I'm working with feels it's important to make fair comparisons, any weight loss must account for the baseline weight.  A logistic transformation seems appropriate, but that term also didn't yield hits I recognized as useful.

Loss of weight --- compare treatments:
Treatment A:  1 - Final weight / Initial weight
Treatment B:  1 - Final weight / Initial weight

This appears to be a situation that would be common, but I'm not framing it in a way that matches an R package.  Any guidance is appreciated.

Regards, Paul


Paul Prew   ▪  Statistician
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