February, 2003
© 2000, 2001, 2003 Scott S. Emerson, M.D., Ph.D.
Frequentist Methods 1: 74
Example
“Pocock” 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   < -2.37   (-0.048,0.048)    > 2.37
 50   < -1.68   (-0.715,0.715)    > 1.68
 75   < -1.37   (-1.011,1.011)    > 1.37
100   < -1.187  (-1.187,1.187)    > 1.187