Boyer 2005.

Methods	Cluster randomized trial: platoons were assigned to study groups. Number of platoons not specified (likely about 30, given 50 to 75 recruits in each platoon and overall sample size) Location: most likely California and South Carolina (USA) Time frame: recruitment June 1999 to June 2000 Sample size calculation (and outcome of focus): originally 477 per group to assess decreasing STI by 6%. Increased to 568 per group to address cluster effect, then increased to 1000 per group since half of participants would be stationed where STI and pregnancy screening not be possible at follow‐up.
Participants	General with N: 2157 women Inclusion criteria: female Marine recruits in training Exclusion criteria: no mention
Interventions	Study focus: preventing STI and unplanned pregnancy Theory or model: Information‐motivation‐behavioral (IMB) skills model Treatment: 4 group sessions (2 hours each) at weeks 1, 2, 4, and 12 of 13‐week recruit training Comparison: same format; content addressed nutrition and physical performance, risk of sports or training injuries, risk and prevention of cervical and breast cancer Duration: 12‐week intervention
Outcomes	Primary: unplanned pregnancy (tested); frequency of condom use; frequency of contraceptive use Secondary: NA Follow‐up: 14 months after baseline
Notes	Additional data from investigator: number of events and group size for pregnancy and condom use
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random numbers table established before study start
Allocation concealment (selection bias)	Low risk	Platoons identified prior to randomization; female Marine recruits in platoons eligible
Blinding of participants and personnel (performance bias) All outcomes	High risk	Platoons informed of group assignment after enrollment and baseline assessment; blinding not feasible due to type of intervention
Blinding of outcome assessment (detection bias)	Unclear risk	No mention
Outcome measures	Unclear risk	Unplanned pregnancy by test; contraceptive use by self‐report
Incomplete outcome data (attrition bias) All outcomes	High risk	Loss to follow‐up: 38% loss for questionnaire data and 59% loss for pregnancy data (due to deployments); study groups were similar.
Other bias	Low risk	Analysis for cluster randomized trial: robust standard errors using Huber‐White sandwich estimator in regression models. Independent variables were intervention group, sexual history, and time between assessments.