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 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. 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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