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

Copas, Andrew; Burkill, Sarah; Conrad, Fred; Couper, Mick P.; Erens, Bob

doi:10.1186/s12874-020-01134-4

Table 3 Estimated prevalence of each of 22 key preselected behaviours in females 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	0.098	0.099	0.095	0.098	0.090	0.092	0.118	0.81	0.76	small	moderate
Both equally willing at first sex	0.791	0.789	0.788	0.794	0.800	0.805	0.821	0.83	0.90	small	small
Contraception used at first sex	0.876	0.870	0.868	0.868	0.871	0.875	0.856	1.19	1.18	small	small
First sex at about the right time	0.566	0.554	0.554	0.563	0.567	0.577	0.644	0.72	0.75	moderate	moderate
Experience not all with opposite sex	0.245	0.233	0.223	0.218	0.207	0.192	0.159	1.72	1.26	large	moderate
Had heterosexual oral sex in last year	0.705	0.714	0.717	0.720	0.739	0.745	0.770	0.71	0.87	moderate	small
Had heterosexual anal sex in last year	0.166	0.168	0.168	0.164	0.172	0.169	0.154	1.09	1.12	small	small
Sex without condom in last 4 weeks	0.789	0.797	0.799	0.798	0.794	0.793	0.800	0.93	0.96	small	small
1+ same gender partners last 5 years	0.064	0.062	0.055	0.052	0.052	0.047	0.049	1.33	0.96	moderate	small
Attended STI clinic in last 5 years	0.184	0.179	0.178	0.179	0.177	0.174	0.203	0.89	0.83	small	small
Attended STI clinic in last year	0.060	0.057	0.056	0.056	0.058	0.056	0.085	0.69	0.64	moderate	moderate
Ever STI diagnosis	0.172	0.176	0.175	0.173	0.163	0.158	0.188	0.90	0.81	small	small
Ever taken illicit drugs	0.406	0.392	0.388	0.380	0.373	0.360	0.385	1.09	0.90	small	small
Ever taken cannabis	0.368	0.353	0.351	0.344	0.339	0.327	0.355	1.06	0.88	small	small
1+ new heterosexual partners last year	0.174	0.168	0.169	0.170	0.166	0.167	0.218	0.76	0.72	moderate	moderate
0 heterosexual partners lifetime	0.059	0.058	0.055	0.057	0.053	0.054	0.045	1.33	1.21	moderate	small
0 heterosexual partners last 5 years	0.099	0.094	0.090	0.090	0.084	0.082	0.064	1.61	1.31	moderate	moderate
0 heterosexual partners last year	0.177	0.168	0.163	0.161	0.148	0.144	0.107	1.79	1.40	large	moderate
Heterosexual sex 5+ occasions last 4 weeks	0.527	0.526	0.524	0.523	0.540	0.542	0.452	1.35	1.43	moderate	moderate
Ever paid for heterosexual sex	0.147	0.155	0.157	0.152	0.150	0.146	0.148	0.99	0.98	small	small
Had a sexual function problem in last year²	0.506	0.496	0.492	0.485	0.460	0.449	0.483	1.10	0.87	small	small
Easy to talk to parent(s) about sex at age 14	0.149	0.148	0.145	0.146	0.154	0.154	0.252	0.52	0.54	large	large

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

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ISSN: 1471-2288

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