February, 2003
© 2000, 2001, 2003 Scott S. Emerson, M.D., Ph.D.
Session 1- Overview: 71
Statistical Issues
The use of a stopping rule allows greater efficiency on average
Sample size requirements are a random variable
·Efficiency characterized by some summary of the sample size distribution
-Average sample N (ASN)
-Median, 75%ile of sample size distribution
-Stopping probabilities at each analysis
Sample size distribution depends on true treatment effect
·(This was the goal of using a stopping rule)