Andrew Copas|Anne M Johnson|J Wadsworth
Assessing participation bias in a sexual behaviour survey
University College London|Mortimer Market Centre|University College London
objectives assess likelihood participation bias large populationbased sex survey possible effect estimates hiv risk behaviours design construction general hypotheses nonparticipants comparisons willing unwilling participants methods british adults aged 1659 years surveyed 19901991 interviews consisted facetoface section combined selfcompletion booklet n 18 876 interviewers recorded interviewee embarrassment homosexual experience number lifetime heterosexual partners grouped 0 1 2 recorded prior booklet offer logistic regression performed embarrassment booklet refusal outcome variables assessing association sexual behaviour controlling demographic variables assuming sexual behaviour nonparticipants closer embarrassed booklet refusers unwilling participants others analyses provide indication nature participation bias results higher refusal embarrassment rates associated reporting homosexual experience fewer heterosexual partners conclusions untestable assumption results consistent nonparticipants generally lower risk hiv infection methods need developed reduce participation bias sex surveys incorporate analysis