February, 2003
© 2000, 2001 Scott S. Emerson, M.D., Ph.D.
Example: Analyses after 40%, 60%,
80%, 100% (maintain power)
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=
131.97) 0.1047 0.3953
Time 2 (N=
197.95) 0.1773 0.3227
Time 3 (N=
263.93) 0.2205 0.2795
Time 4 (N=
329.91) 0.2500 0.2500