February, 2003
© 2000, 2001 Scott S. Emerson, M.D., Ph.D.
Example: Analyses after 20%, 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= 72.10) -0.0590 0.5590
Time 2 (N=
144.20) 0.1047 0.3953
Time 3 (N=
216.31) 0.1773 0.3227
Time 4 (N=
288.41) 0.2205 0.2795
Time 5 (N=
360.51) 0.2500 0.2500