I am having trouble with a power analysis for these 2 types of models. I am trying to assess how pregnancy weight gain (<10 lbs and >40 lbs vs 20-29 lbs) affects benign breast disease.
However, there really isn't any preliminary data on this and consequently I am not sure how to go about getting the Pr(Y=1|X=1) under H0 and H1 for logistic regression. I do not have data on the proportion of people falling into each of the 3 bins but I assume that they are not roughly equal as most women gain the referent amount of weight (20-40lbs max).
I have the same problem with my Cox proportional hazards model: How does the timing at which food is consumed (<3 months of age and >6 months vs 3-6 months of age) affect diabetes (yes/no)? I do have data on these proportions and they are approximately 27%, 44%, 27%. Any help would be appreciated!!