Find who a study could not observe

Inputs: [STUDY METHODS], [TARGET POPULATION], [RECRUITMENT NOTES]. Trace eligibility, recruitment channels, nonresponse and exclusions. Distinguish measured participants from the wider group of interest. Output: A coverage map, bias hypotheses and follow-up data needs. Check: No bias direction is claimed without supporting evidence. If essential information is missing, identify it rather than filling the gap with a guess. Name the populations absent from the frame separately from those invited but not responding.