February, 2003
© 2000, 2001, 2003 Scott S. Emerson, M.D., Ph.D.
Frequentist Methods 1: 73
Example
“O’Brien-Fleming” stopping rule
At each interim analysis, stop early if sample mean is indicated range
At the final analysis, the stopping must occur
 N      Harm        Equiv        Efficacy
 25   < -4.09         ----        > 4.09
 50   < -2.05   (-0.006,0.006)    > 2.05
 75   < -1.36   (-0.684,0.684)    > 1.36
100   < -1.023  (-1.023,1.023)    > 1.023