I want to find the sample size for logistic regression where I have a covariate with 15 levels and the covariates interacts with time, which means that the effect of the covariates is different for different periods of times. Can anyone help me find the sample size and effect size? I wish I could do this using simulations. Is there a code in SAS or R?

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    $\begingroup$ I've changed your sample-size tag to power-analysis, but I'm not 100% sure this is what you're trying to do. In power analysis, you can find the required sample size to reject a null hypothesis of zero effect given an effect of a size you would expect to find, but I'm not sure how you could find both the sample size AND the effect size without knowing one or the other. $\endgroup$ – Nick Stauner Mar 14 '14 at 11:12
  • $\begingroup$ SAS proc power can accommodate logistic regression. $\endgroup$ – Penguin_Knight Mar 14 '14 at 12:29

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