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Table 2 Estimated prevalence of each of 22 key preselected behaviours in males in the best performing survey (WS-B2), before and after PSA weighting in five stages and in Natsal-3 for comparison, odds ratios and bias assessment

From: An evaluation of whether propensity score adjustment can remove the self-selection bias inherent to web panel surveys addressing sensitive health behaviours

  Proportions by weighting scheme and in Natsal-3 Odds ratios relative to Natsal-3 Bias3 relative to Natsal-3
Behaviour Age-sex PSA 1 PSA 2 PSA 3 PSA 4 PSA 5 Natsal-3 Age-sex PSA5 Age-sex PSA5
‘Binge’ drinks once a week or more1 0.170 0.168 0.163 0.167 0.162 0.165 0.214 0.75 0.73 moderate moderate
Both equally willing at first sex 0.882 0.886 0.888 0.890 0.901 0.899 0.911 0.73 0.87 moderate small
Contraception used at first sex 0.864 0.864 0.872 0.868 0.872 0.864 0.820 1.39 1.39 moderate moderate
First sex at about the right time 0.608 0.623 0.622 0.633 0.648 0.641 0.743 0.54 0.62 large moderate
Experience not all with opposite sex 0.162 0.155 0.119 0.119 0.110 0.089 0.072 2.49 1.26 large moderate
Had heterosexual oral sex in last year 0.715 0.727 0.742 0.747 0.746 0.747 0.793 0.65 0.77 moderate moderate
Had heterosexual anal sex in last year 0.204 0.203 0.202 0.211 0.197 0.202 0.176 1.20 1.19 small small
Sex without condom in last 4 weeks 0.769 0.779 0.781 0.776 0.791 0.790 0.749 1.12 1.26 small moderate
1+ same gender partners last 5 years 0.079 0.076 0.046 0.050 0.045 0.036 0.030 2.77 1.21 large small
Attended STI clinic in last 5 years 0.143 0.141 0.128 0.128 0.125 0.134 0.187 0.73 0.67 moderate moderate
Attended STI clinic in last year 0.058 0.055 0.046 0.046 0.046 0.049 0.069 0.83 0.70 small moderate
Ever STI diagnosis 0.123 0.126 0.119 0.116 0.105 0.113 0.133 0.91 0.83 small small
Ever taken illicit drugs 0.446 0.459 0.456 0.451 0.448 0.446 0.523 0.73 0.73 moderate moderate
Ever taken cannabis 0.407 0.419 0.416 0.410 0.410 0.409 0.491 0.71 0.72 moderate moderate
1+ new heterosexual partners last year 0.247 0.236 0.232 0.238 0.222 0.222 0.274 0.87 0.76 small moderate
0 heterosexual partners lifetime 0.116 0.099 0.088 0.087 0.086 0.089 0.060 2.06 1.53 large moderate
0 heterosexual partners last 5 years 0.143 0.124 0.107 0.107 0.106 0.109 0.077 2.00 1.47 large moderate
0 heterosexual partners last year 0.200 0.183 0.165 0.167 0.157 0.161 0.112 1.98 1.52 large moderate
Heterosexual sex 5+ occasions last 4 weeks 0.511 0.520 0.519 0.528 0.546 0.550 0.464 1.21 1.41 small moderate
Ever paid for heterosexual sex 0.132 0.129 0.128 0.125 0.117 0.117 0.104 1.31 1.14 moderate small
Had a sexual function problem in last year2 0.437 0.433 0.423 0.411 0.397 0.396 0.395 1.19 1.00 small small
Easy to talk to parent(s) about sex at age 14 0.161 0.153 0.151 0.160 0.162 0.167 0.184 0.85 0.89 small small
  1. 1. Defined as drinking 6+ units of alcohol; 2. Based on half the sample only; 3. Small bias is an odds ratio relative to Natsal-3 in the range 0.8–1.25, moderate bias is in the range 0.6–0.8 or 1.25–1.67, large bias otherwise