February, 2003
© 2000, 2001, 2003 Scott S. Emerson, M.D., Ph.D.
Frequentist Methods 1: 85
Example
“O’Brien-Fleming” stopping rule with desired power
At each interim analysis, stop early if sample mean is indicated range
At the final analysis, the stopping must occur
 N      Harm        Equiv        Efficacy
 26   < -4.01         ----        > 4.09
 52   < -2.01   (-0.006,0.006)    > 2.01
 78   < -1.34   (-0.670,0.670)    > 1.34
104   < -1.003  (-1.003,1.003)    > 1.023