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?

    Thanks and regards,

     Xing

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