J
NIH Power Calculations 1
|
1 |
Reprinted with permission from the June 28, 1993 WHI Protocol, pages 77-83. |
(i) ERT versus Control: Coronary Heart Disease.
|
Power (%) |
||||||
|
Percentage cases |
Total sample size |
|||||
|
Average follow-up (y) |
Intervention effect (%) |
Control |
ERT (or PERT) |
20,000 |
25,000 |
30,000 |
|
6 |
25 |
3.26 |
2.71 |
50 |
59 |
67 |
|
30 |
3.26 |
2.62 |
66 |
76 |
83 |
|
|
35 |
3.25 |
2.49 |
80 |
88 |
93 |
|
|
9 |
25 |
5.03 |
4.16 |
69 |
79 |
86 |
|
30 |
5.02 |
3.97 |
85 |
92 |
96 |
|
|
35 |
5.01 |
3.79 |
94 |
98 |
99 |
|
(ia) PERT versus Control: Coronary Heart Disease.
|
Power (%) |
||||||
|
Percentage cases |
Total sample size |
|||||
|
Average follow-up (y) |
Intervention effect (%) |
Control |
PERT |
20,000 |
25,000 |
30,000 |
|
6 |
25 |
3.26 |
2.71 |
48 |
57 |
65 |
|
30 |
3.26 |
2.60 |
64 |
74 |
82 |
|
|
35 |
3.25 |
2.49 |
79 |
87 |
92 |
|
|
9 |
25 |
5.03 |
4.16 |
67 |
77 |
84 |
|
30 |
5.02 |
3.97 |
84 |
91 |
95 |
|
|
35 |
5.01 |
3.79 |
94 |
97 |
99 |
|
(ii) ERT versus Control: Combined Fractures.
(The percentage of cases and the powers in this table are based upon our original age distribution assumptions, i.e., 50-59, 60-69, 70-79 year olds enter in the ratio 2:2:1, and hence are conservative estimates.)
|
Power (%) |
||||||
|
Percentage cases |
Total sample size |
|||||
|
Average follow-up (y) |
Intervention effect (%) |
Control |
ERT |
20,000 |
25,000 |
30,000 |
|
6 |
25 |
5.84 |
4.86 |
79 |
87 |
92 |
|
30 |
5.84 |
4.66 |
92 |
96 |
98 |
|
|
35 |
5.83 |
4.46 |
98 |
99 |
>99 |
|
|
9 |
25 |
8.85 |
7.31 |
94 |
97 |
99 |
|
30 |
8.84 |
6.99 |
99 |
>99 |
>99 |
|
|
35 |
8.82 |
6.66 |
>99 |
>99 |
>99 |
|
(iia) ERT versus Control: Combined Fractures.
(The percentage of cases and the powers in this table are based upon our original age distribution assumptions, i.e., 50-59, 60-69, 70-79 year olds enter in the ratio 2:2:1, and hence are conservative estimates.)
|
Power (%) |
||||||
|
Percentage cases |
Total sample size |
|||||
|
Average follow-up (y) |
Intervention effect (%) |
Control |
PERT |
20,000 |
25,000 |
30,000 |
|
6 |
25 |
5.84 |
4.86 |
77 |
85 |
91 |
|
30 |
5.84 |
4.66 |
90 |
95 |
98 |
|
|
35 |
5.83 |
4.46 |
98 |
99 |
>99 |
|
|
9 |
25 |
8.85 |
7.31 |
93 |
97 |
99 |
|
30 |
8.84 |
6.99 |
99 |
>99 |
>99 |
|
|
35 |
8.82 |
6.66 |
>99 |
>99 |
>99 |
|
(iii) ERT versus Control: Hip Fractures.
|
Power (%) |
||||||
|
Percentage cases |
Total sample size |
|||||
|
Average follow-up (y) |
Intervention effect (%) |
Control |
ERT |
20,000 |
25,000 |
30,000 |
|
6 |
25 |
2.34 |
1.94 |
41 |
49 |
56 |
|
30 |
2.34 |
1.86 |
55 |
65 |
73 |
|
|
35 |
2.33 |
1.77 |
70 |
79 |
86 |
|
|
9 |
25 |
3.91 |
3.22 |
62 |
71 |
79 |
|
30 |
3.90 |
3.07 |
78 |
87 |
92 |
|
|
35 |
3.89 |
2.92 |
90 |
95 |
98 |
|
(iiia) PERT versus Control: Hip Fractures.
|
Power (%) |
||||||
|
Percentage cases |
Total sample size |
|||||
|
Average follow-up (y) |
Intervention effect (%) |
Control |
PERT |
20,000 |
25,000 |
30,000 |
|
6 |
25 |
2.34 |
1.94 |
39 |
47 |
54 |
|
30 |
2.34 |
1.86 |
54 |
63 |
71 |
|
|
35 |
2.33 |
1.77 |
68 |
77 |
84 |
|
|
9 |
25 |
3.91 |
3.22 |
60 |
69 |
77 |
|
30 |
3.90 |
3.07 |
76 |
85 |
91 |
|
|
35 |
3.89 |
2.92 |
88 |
94 |
97 |
|
(iv) ERT versus Control: Breast Cancer.
|
Power (%) |
||||||
|
Percentage Cases |
Total Sample Size |
|||||
|
Average follow-up (y) |
Increase due to ERT (%) |
Control |
ERT |
20,000 |
25,000 |
30,000 |
|
6 |
20 |
2.07 |
2.25 |
13 |
15 |
17 |
|
30 |
2.08 |
2.35 |
23 |
28 |
32 |
|
|
9 |
20 |
3.04 |
3.40 |
27 |
33 |
38 |
|
30 |
3.05 |
3.60 |
52 |
61 |
69 |
|
|
14 |
20 |
4.5 |
5.17 |
52 |
62 |
70 |
|
30 |
4.53 |
5.54 |
85 |
92 |
96 |
|
(iva) PERT versus Control: Breast Cancer.
|
Power (%) |
||||||
|
Percentage Cases |
Total Sample Size |
|||||
|
Average follow-up (y) |
Increase due to PERT (%) |
Control |
20,000 |
ERT |
25,000 |
30,000 |
|
6 |
20 |
2.07 |
2.25 |
12 |
14 |
16 |
|
30 |
2.08 |
2.35 |
22 |
27 |
31 |
|
|
9 |
20 |
3.04 |
3.40 |
26 |
32 |
37 |
|
30 |
3.05 |
3.60 |
50 |
60 |
67 |
|
|
14 |
20 |
4.50 |
5.17 |
51 |
60 |
68 |
|
30 |
4.53 |
5.54 |
83 |
91 |
95 |
|
(i) Dietary Modification: Breast Cancer.
|
Power (%) |
||||||
|
Percentage of cases |
Sample size |
|||||
|
Average follow-up (y) |
Intervention effect (%) |
Control |
Intervention |
42,000 |
48,000 |
54,000 |
|
6 |
11 |
2.05 |
1.89 |
25 |
28 |
31 |
|
12 |
2.05 |
1.87 |
32 |
35 |
39 |
|
|
14 |
2.05 |
1.85 |
39 |
44 |
48 |
|
|
9 |
11 |
2.92 |
2.61 |
58 |
63 |
69 |
|
12 |
2.92 |
2.57 |
70 |
75 |
80 |
|
|
14 |
2.92 |
2.52 |
81 |
86 |
89 |
|
(ii) Dietary Modification: Colorectal Cancer.
|
Power (%) |
||||||
|
Percentage of cases |
Sample size |
|||||
|
Average follow-up (y) |
Intervention effect (%) |
Control |
Intervention |
42,000 |
48,000 |
54,000 |
|
6 |
18 |
1.07 |
0.93 |
33 |
37 |
41 |
|
20 |
1.07 |
0.92 |
40 |
45 |
49 |
|
|
22 |
1.07 |
0.91 |
47 |
52 |
57 |
|
|
9 |
18 |
1.61 |
1.32 |
77 |
83 |
87 |
|
20 |
1.61 |
1.29 |
86 |
90 |
93 |
|
|
22 |
1.60 |
1.25 |
92 |
95 |
97 |
|
(iii) Dietary Modification: Coronary Heart Disease.
|
Power (%) |
||||||
|
Percentage of cases |
Sample size |
|||||
|
Average follow-up (y) |
Intervention effect |
Control |
Intervention |
42,000 |
48,000 |
54,000 |
|
6 |
11 |
3.04 |
2.72 |
48 |
53 |
58 |
|
12 |
3.03 |
2.67 |
58 |
64 |
69 |
|
|
14 |
3.02 |
2.63 |
68 |
74 |
79 |
|
|
9 |
11 |
4.62 |
4.15 |
62 |
67 |
72 |
|
12 |
4.60 |
4.08 |
72 |
78 |
83 |
|
|
14 |
4.58 |
4.00 |
82 |
86 |
90 |
|
(i) Calcium/Vitamin D versus Control: Hip Fractures
|
Power (%) |
||||||
|
Percentage cases |
Total sample size |
|||||
|
Average Follow-up (y) |
Intervention effect (%) |
Control |
ERT (or PERT) |
20,000 |
25,000 |
30,000 |
|
5 |
25 |
1.88 |
1.58 |
53 |
67 |
78 |
|
30 |
1.88 |
1.51 |
69 |
83 |
91 |
|
|
35 |
1.88 |
1.45 |
83 |
93 |
97 | |
|
8 |
25 |
3.35 |
2.76 |
81 |
92 |
97 |
|
30 |
3.34 |
2.64 |
93 |
98 |
>99 |
|
|
35 |
3.34 |
2.51 |
98 |
>99 |
>99 |
|
(ii) Calcium/Vitamin D versus Control: Combined Fractures
(The percentages of cases and powers in this table are based upon our original age distribution assumptions i.e., 50-59, 60-69, 70-79 year olds enter in the ratio 2.2.1 and hence are conservative estimates.)
|
Power (%) |
||||||
|
Percentage cases |
Total sample size |
|||||
|
Average Follow-up (y) |
Intervention effect (%) |
Control |
Calcium/ Vitamin D |
25,000 |
35,000 |
45,000 |
|
5 |
25 |
4.84 |
4.07 |
90 |
97 |
99 |
|
30 |
4.84 |
3.91 |
98 |
>99 |
>99 |
|
|
35 |
4.83 |
3.75 |
>99 |
>99 |
>99 |
|
|
8 |
25 |
7.85 |
6.49 |
99 |
>99 |
>99 |
|
30 |
7.83 |
6.20 |
>99 |
>99 |
>99 |
|
|
35 |
7.82 |
5.91 |
>99 |
>99 |
>99 |
|
(iii) Calcium/Vitamin D versus Control: Colorectal Cancer
|
Power (%) |
||||||
|
Percentage cases |
Total sample size |
|||||
|
Average Follow-up (y) |
Intervention effect (%) |
Control |
Calcium/ Vitamin D |
25,000 |
35,000 |
45,000 |
|
5 |
18 |
0.86 |
0.76 |
17 |
23 |
28 |
|
20 |
0.86 |
0.75 |
20 |
27 |
33 |
|
|
22 |
0.86 |
0.74 |
24 |
31 |
38 |
|
|
8 |
25 |
1.42 |
1.17 |
52 |
66 |
77 |
|
30 |
1.42 |
1.15 |
60 |
75 |
85 |
|
|
35 |
1.42 |
1.12 |
69 |
83 |
91 |
|
