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Example for sample size calculation
| Type of progression | PID incidence (per year) in control groupa | Relative riska | Sample size needed per group |
|---|---|---|---|
| Immediate progression | 0.007 | 1.05 | 1,071,082 |
| Constant progression | 0.007 | 0.42 | 4,654 |
| Progression at the end | 0.007 | 0.39 | 4,123 |
aBaseline values of Table 1 ‘General sample size calculation’ have been used for all types of progression
PID, pelvic inflammatory disease
