Table 1

Determination of the sample size: based on an estimated 15% ventilator-associated pneumonia rate, 2650 patients (n=1325 in each arm) will be required to detect a 25% relative risk reduction with 80% power

Baseline riskRelative risk reduction
10%15%20%25%30%
8%17 4737635422126531809
9%15 3746720371623371594
10%13 6955988331320841422
12%11 1764891270717041164
14%9377410722751433979
15%865737932102 1325 906
16%8028351919511230841
18%6978306116991072734
20%613926951497945647
22%545223961332842577
24%487921471194756518
25%462720371134718493
30%36201598892566389
35%29001284719458316
40%23611049589376260
50%1605719408262183

  • Per group  sample size for  80%  power and  alpha=0.05 , using continuity correction.

  • Bolded value represents the value selected for sample size.