Sample size estimation for parallel design [Power / Sample Size]

posted by Nav Coelho – 2007-07-20 18:14 (5981 d 16:26 ago) – Posting: # 916
Views: 25,316

Dear all,

I have data from a parallel pilot study and am using that to estimate the sample size for a pivotal study. The formula that I am using requires an estimate of the inter subject variability which I don't have. I have the total variability (sqrt(MSE)). Is there a way to estimate intersubject variability from a parallel design or would it be correct to use the total variability instead?

Would it be correct to estimate inter-subject var as sd/mean for test and reference separately and then take the average?

And one last question, how correct is it to take 60% of inter subject (calculated as sd/mean) to be the intrasubject variability?

Thanks in Advance!
Nav Coelho

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