February, 2003
© 2000, 2001, 2003 Scott S. Emerson, M.D., Ph.D.
“O’Brien-Fleming” stopping rule
Possibility for early stopping introduces jump discontinuities
at values corresponding to stopping boundaries
·Size
of jump will depend upon true value of the treatment effect (mean)
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