February, 2003
© 2000, 2001 Scott S. Emerson, M.D., Ph.D.
Example: Stopping rule chosen at
first analysis (with estimates for later analyses)
One-sided test
of a greater alternative:
Null : Theta <= 0
(size = 0.025)
Alt : Theta >=
0.5 (power = 0.975)
(Emerson & Fleming (1989) symmetric test)
STOPPING BOUNDARIES: Sample Mean scale
a d
Time 1 (N= 77.08) -0.0743 0.5744
Time 2 (N=
154.16) 0.1211 0.3789
Time 3 (N=
231.23) 0.2029 0.2971
Time 4 (N=
308.31) 0.2500 0.2500