February, 2003
© 2000, 2001  Scott S. Emerson, M.D., Ph.D.
Session 2: 99
Unified Design Family
Parameterization of boundary shape function includes many previously described approaches
Wang & Tsiatis Boundary Shape Functions:
·A*  =     0,  R*  =     0, P*  >     0  
·P* measures early conservatism
-P*  =  0.5   Pocock (1977)
-P*  =  1.0   O’Brien-Fleming (1979)
·(P* = ¥ precludes early stopping)