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. Author manuscript; available in PMC: 2011 Jun 15.
Published in final edited form as: Stat Med. 2010 Jun 15;29(13):1377–1387. doi: 10.1002/sim.3892

Table 2.

Sample Size Requirements for a Random 2nd Stage Exposure Sample within a Large Cohort Study.

ψYX (ψ Y(X95/X50)) ρXZ 100,000 Cohort Size 75,000 Cohort Size
PY = 0.0025 PY = 0.005 PY = 0.01 PY = 0.025 PY = 0.05 PY = 0.0025 PY = 0.005 PY = 0.01 PY = 0.025 PY = 0.05
1.05 (1.10) 0.00 1322202 662777 333075 135294 69439 1322202 662777 333075 135294 69439
0.10 69104 69383
0.30 66386 68889
0.50 59209 67586
0.70 39990 64097
0.90 13 45737
1.10 (1.205) 0.00 346504 173699 87300 35472 18214 346504 173699 87300 35472 18214
0.10 87169 34820 17391 35072 17642
0.30 86041 29097 10167 31565 12617
0.50 83063 14005 86 22309 485
0.70 75091 30 14 217 17
0.90 33104 4 3 5 3
1.25 (1.549) 0.00 63232 31709 15947 6492 3343 63232 31709 15947 6492 3343
0.10 62866 31022 15102 5570 2457 63118 31274 15353 5812 2668
0.30 59603 24967 7696 254 121 62074 27434 10135 610 147
0.50 50989 9021 65 32 28 59317 17304 151 36 29
0.70 27940 24 13 10 9 51940 60 15 10 10
0.90 9 4 3 3 2 13134 4 3 3 2
1.50 (2.214) 0.00 19169 9622 4849 1985 1032 19169 9622 4849 1985 1032
0.10 18355 8720 3930 1243 602 18606 8968 4163 1385 645
0.30 11212 1249 163 98 85 13665 3287 244 107 88
0.50 100 39 30 26 25 1088 49 32 27 25
0.70 14 11 10 9 9 18 12 10 9 9
0.90 3 3 2 2 2 3 3 3 2 2

ψY(X95/X50) corresponds to the increased odds of the health outcome based on a comparison of the 95th percentile of exposure to the 50th percentile of exposure.