February, 2003
© 2000, 2001, 2003 Scott S. Emerson, M.D., Ph.D.
Frequentist Methods 1: 55
Example
“Pocock” stopping rule
We can consider an alternative stopping rule that is less conservative at the interim analyses
·(This stopping rule is similar to the previous one except it uses Pocock (1977) boundary relationships)
 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