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Table 1 Sample size determination

From: Creative solutions to extraordinary challenges in clinical trials: methodology of a phase III trial of azithromycin and chloroquine fixed-dose combination in pregnant women in Africa

Observed pooled proportion for the primary endpoint at N = 1,000

Total sample size required

≤0.28

5,044

>0.28 to ≤0.32

4,206

>0.32 to ≤0.36

3,552

>0.36 to ≤0.40

3,030

>0.40

2,602

  1. The design assumed a 20% risk reduction in the primary endpoint (relative risk = 0.80, fixed-dose combination of azithromycin and chloroquine/sulphadoxine-pyrimethamine [AZCQ/SP]). A 23% risk reduction (relative risk = 0.77, AZCQ/SP) was assumed for low birth weight (key secondary endpoint).