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Unconditional and conditional monetary incentives to increase response to mailed questionnaires: A randomized controlled study within a trial (SWAT)

Young, Ben; Bedford, Laura; das Nair, Roshan; Gallant, Stephanie; Littleford, Roberta; Robertson, John F.R.; Schembri, Stuart; Sullivan, Frank M.; Vedhara, Kavita; Kendrick, Denise; ECLS Study Team

Authors

Ben Young

Laura Bedford

ROSHAN NAIR Roshan.dasnair@nottingham.ac.uk
Professor of Clinical Psychology and Neuropsychology

Stephanie Gallant

Roberta Littleford

Stuart Schembri

Frank M. Sullivan

KAVITA VEDHARA kavita.vedhara@nottingham.ac.uk
Professor in Applied Psychology

DENISE KENDRICK denise.kendrick@nottingham.ac.uk
Professor of Primary Care Research

ECLS Study Team



Abstract

Rationale, aims, and objectives: High response rates to research questionnaires can help to ensure results are more representative of the population studied and provide increased statistical power, on which the study may have been predicated. Improving speed and quality of response can reduce costs.

Method: We conducted a randomised Study Within A Trial (SWAT) to assess questionnaire response rates, reminders sent and data completeness with unconditional compared to conditional monetary incentives. Eligible individuals were mailed a series of psychological questionnaires as a follow-up to a baseline host trial questionnaire. Half received a £5 gift voucher with questionnaires (unconditional) and half were promised the voucher after returning questionnaires (conditional).

Results: Of 1079 individuals, response rates to the first follow-up questionnaire were 94.2% and
91.7% in the unconditional and conditional monetary incentive groups respectively (OR 1.78, 95% CI
0.85 to 3.72). There were significantly greater odds of returning repeat questionnaires in the unconditional group at six months (OR 2.97, 95% CI 1.01 to 8.71; p = 0.047) but not at 12 months
(OR 1.12, 95% CI 0.44 to 2.85). Incentive condition had no impact at any time point on the proportion of sent questionnaires that needed reminders. Odds of incomplete questionnaires were significantly greater at three months in the unconditional compared to the conditional incentive group (OR 2.45, 95% CI 1.32 to 4.55; p = 0.004).

Conclusions: Unconditional monetary incentives can produce a transitory greater likelihood of mailed questionnaire response in a clinical trial participant group, consistent with the direction of effect in other settings. However, this could have been a chance finding. The use of multiple strategies to promote response may have created a ceiling effect. This strategy has potential to reduce administrative and postage costs, weighed against the cost of incentives used, but could risk compromising the completeness of data.

Citation

Young, B., Bedford, L., das Nair, R., Gallant, S., Littleford, R., Robertson, J. F., …ECLS Study Team, . (2020). Unconditional and conditional monetary incentives to increase response to mailed questionnaires: A randomized controlled study within a trial (SWAT). Journal of Evaluation in Clinical Practice, 26(3), 893-902. https://doi.org/10.1111/jep.13230

Journal Article Type Article
Acceptance Date Jun 16, 2019
Online Publication Date Jul 22, 2019
Publication Date 2020-06
Deposit Date Jun 18, 2019
Publicly Available Date Jul 23, 2020
Journal Journal of Evaluation in Clinical Practice
Print ISSN 1356-1294
Electronic ISSN 1365-2753
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 26
Issue 3
Pages 893-902
DOI https://doi.org/10.1111/jep.13230
Keywords Public Health, Environmental and Occupational Health; Health Policy
Public URL https://nottingham-repository.worktribe.com/output/2204208
Publisher URL https://onlinelibrary.wiley.com/doi/abs/10.1111/jep.13230
Additional Information This is the peer reviewed version of the following article: Young, B, Bedford, L, das Nair, R, et al. Unconditional and conditional monetary incentives to increase response to mailed questionnaires: A randomized controlled study within a trial (SWAT). J Eval Clin Pract. 2019; 1– 10. , which has been published in final form at https://doi.org/10.1111/jep.13230. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

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