Sample size considerations using mathematical models: an example with Chlamydia trachomatis infection and its sequelae pelvic inflammatory disease

Table 2 Example for sample size calculation

Type of progression	PID incidence (per year) in control group^a	Relative risk^a	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

ISSN: 1471-2334