Table 3 Sample size calculation for the prospective survey
Significance level | Power | % of outcome in unexposed | Effect size (relative risk) | Attrition | Sample size for women at risk of unintended pregnancy at baseline | Overall sample size |
|---|---|---|---|---|---|---|
0.05 | 80% | 30% | 30% (0.7) | 45% | 1998 | 2597 |