Response is increased using postal rather than electronic questionnaires – new results from an updated Cochrane Systematic Review

Abstract Background Paper questionnaires are more common in epidemiology than those administered online, but increasing Internet access may change this. Researchers planning to use a self-administered questionnaire should know whether response rates to questionnaires administered electronically differ to those of questionnaires administered by post. We analysed trials included in a recently updated Cochrane Review to answer this question. Methods We exported data of randomised controlled trials included in three comparisons in the Cochrane Review that had evaluated hypotheses relevant to our research objective and imported them into Stata for analysis. We pooled odds ratios for response in random effects meta-analyses. We explored causes of heterogeneity among study results using subgroups. We assessed evidence for reporting bias using Harbord's modified test for small-study effects. Results Twenty-seven trials (66,118 participants) evaluated the effect on response of an electronic questionnaire compared with postal. Results were heterogeneous (I-squared=98%). Synthesis of studies at low risk of bias indicates that response was increased (OR=1.43; 95% CI 1.08–1.89) using postal questionnaires. Ten trials (39,523 participants) evaluated the effect of providing a choice of mode (postal or electronic) compared to an electronic questionnaire only. Response was increased with a choice of mode (OR=1.63; 95% CI 1.18–2.26). Eight trials (20,909 participants) evaluated the effect of a choice of mode (electronic or postal) compared to a postal questionnaire only. There was no evidence for an effect on response (OR=0.94; 95% CI 0.86–1.02). Conclusions Postal questionnaires should be used in preference to, or offered in addition to, electronic modes.