Ho: margin ≤ delta Ha: margin > delta
if delta >0, the rejection of Null Hypothesis indicates the superiority of the test over the control;
if delta <0, the rejection of the null hypothesis implies the non-inferiority of the test against the control.
power = 1-beta
pooled standard deviation of two groups
Example: k=2 indicates a 1 to 2 test-control allocation.
the superiority or non-inferiority margin
the true mean difference between a test mu2 and a control mu1
Chow SC, Shao J, Wang H. Sample Size Calculation in Clinical Research. New York: Marcel Dekker, 2003