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Table 2 Phase I and phase II sample power.

From: Genetic factors leading to chronic Epstein-Barr virus infection and nasopharyngeal carcinoma in South East China: Study design, methods and feasibility

     Phase I Phase II All
     Case/control Power Case/control Power Case/control Power
NPC+vs IgA+     350/288   1024/1009   1374/1297  
  OR 0.75 1.5   17%   64%   79%
   0.50 2.0   62%   > 99%   > 99%
   0.33 3.0   98%   > 99%   > 99%
IgA+ vs IgA-     288/346   1009/1022   1297/1368  
  OR 0.75 1.5   18%   64%   79%
   0.50 2.0   64%   99%   > 99%
   0.33 3.0   99%   > 99%   > 99%
NPC+/IgA+ vs IgA-    638/346   2033/1022   2671/1368  
  OR 0.75 1.5   25%   77%   90%
   0.50 2.0   78%   > 99%   > 99%
   0.33 3.0   > 99%   > 99%   > 99%
  1. Note. Allele frequency = 10 per cent; Type 1 error = 1 per cent.
  2. Power calculated for a 10% allele frequency, dominant genetic model and a p value of ≤ 0.01 for given case and control numbers using a two-tailed test. For example, with the Phase I cases/controls available, we would discover a genetic association of strength OR = 1.5, only 14% of the time, but a stronger gene (OR = 3.0) would be detected 96% of the time with available patient numbers.
  3. Abbreviations: IgA, immunoglobulin A; NPC, nasopharyngeal carcinoma.