Skip to main content
. Author manuscript; available in PMC: 2021 Aug 13.
Published in final edited form as: Revstat Stat J. 2017 Jul;15(3):373–394.

Table 2:

Statistical power and average time to signal, when the null hypothesis is rejected, for the Poisson based maximized SPRT when a minimum of M events is required before the null hypothesis can be rejected. T is the upper limit on the sample size (length of surveillance), expressed in terms of the expected number of events under the null. The type 1 error is α = 0.05.

Statistical Power Average Time to Signal
T M RR=1.5 2 3 4 10 RR=1.5 2 3 4 10
1 1 0.107 0.185 0.379 0.573 0.987 0.30 0.35 0.39 0.39 0.22
1 3 0.129 0.234 0.466 0.665 0.993 0.59 0.58 0.55 0.51 0.30
2 1 0.130 0.255 0.561 0.799 1.000 0.63 0.75 0.79 0.73 0.24
2 3 0.157 0.315 0.645 0.857 1.000 0.92 0.94 0.89 0.78 0.31
5 1 0.190 0.447 0.876 0.987 1.000 1.82 2.09 1.78 1.22 0.26
5 3 0.224 0.507 0.905 0.991 1.000 2.10 2.17 1.73 1.17 0.31
5 6 0.255 0.559 0.928 0.994 1.000 2.71 2.58 2.05 1.54 0.60
10 1 0.280 0.685 0.989 1.000 1.000 4.02 4.13 2.45 1.35 0.27
10 3 0.321 0.733 0.993 1.000 1.000 4.25 4.07 2.31 1.30 0.32
10 6 0.358 0.770 0.995 1.000 1.000 4.71 4.25 2.50 1.61 0.60
10 10 0.391 0.803 0.996 1.000 1.000 5.67 5.03 3.40 2.50 1.00
20 1 0.450 0.921 1.000 1.000 1.000 8.68 6.96 2.67 1.41 0.28
20 3 0.492 0.936 1.000 1.000 1.000 8.65 6.62 2.53 1.37 0.33
20 6 0.531 0.948 1.000 1.000 1.000 8.92 6.57 2.69 1.65 0.60
20 10 0.562 0.957 1.000 1.000 1.000 9.47 6.96 3.50 2.51 1.00
50 1 0.803 1.000 1.000 1.000 1.000 20.45 8.94 2.82 1.48 0.30
50 3 0.829 1.000 1.000 1.000 1.000 19.82 8.45 2.71 1.45 0.33
50 6 0.847 1.000 1.000 1.000 1.000 19.41 8.24 2.86 1.71 0.60
50 10 0.863 1.000 1.000 1.000 1.000 19.35 8.46 3.59 2.52 1.00
100 1 0.978 1.000 1.000 1.000 1.000 29.93 9.30 2.92 1.53 0.31
100 3 0.982 1.000 1.000 1.000 1.000 28.52 8.87 2.82 1.51 0.34
100 6 0.985 1.000 1.000 1.000 1.000 27.58 8.71 2.97 1.75 0.60
100 10 0.987 1.000 1.000 1.000 1.000 27.04 8.93 3.65 2.53 1.00
200 1 1.000 1.000 1.000 1.000 1.000 33.00 9.62 3.01 1.58 0.32
200 3 1.000 1.000 1.000 1.000 1.000 31.47 9.25 2.93 1.56 0.35
200 6 1.000 1.000 1.000 1.000 1.000 30.47 9.11 3.07 1.78 0.60
200 10 1.000 1.000 1.000 1.000 1.000 29.88 9.33 3.71 2.54 1.00