Dear R users: How to calculate the sample size with ANCOVA? For example, in a clinical trial, the correlation between the baseline and one-year follow-up blood pressure is 0.7, with a standrad devision 15, in order to detect a 10 difference between baseline and follow-up with a power = 0.9, and alpha = 0.05? Then, how to calculate the sample size with the correlation of 0.7 between baseline and follow-up?
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