Article
Does a photography of the researcher on the invitation letter affect the recruitment rate? A study within a trial
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Authors
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Barbara Prediger
- Universität Witten/Herdecke, IFOM – Institut für Forschung in der Operativen Medizin, Deutschland
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Nadja Könsgen
- Universität Witten/Herdecke, IFOM – Institut für Forschung in der Operativen Medizin, Deutschland
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Käthe Gooßen
- Universität Witten/Herdecke, IFOM – Institut für Forschung in der Operativen Medizin, Deutschland
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Dawid Pieper
- Universität Witten/Herdecke, IFOM – Institut für Forschung in der Operativen Medizin, Deutschland
| Published: | February 23, 2021 |
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Outline
Text
Background/research question: Recruitment is one of the main issues in any research that depends on participant involvement. Previous studies suggests that the use of an attractive color photograph of the researcher increases responses to postal questionnaires [1], [2]. This study within a trial (SWAT) aims to assess whether invitation letters including researcher photographs increase the recruitment rate in the context of a survey on medical second opinions.
Methods: We registered our SWAT at Queens University Belfast (SWAT 104). Through 25 local register offices, we identified a random sample of 9,990 persons. For selection of participants, we used 1:1:1 disproportionate stratified sampling with settlement pattern (urban area, area with agglomeration, rural area) as the stratification variable. We randomly assigned our sample to the intervention group (IG) and control group (CG) in a 1:1 ratio. The IG received an invitation letter with a photograph of both researchers, and the CG received an invitation letter without photograph. We had originally planned to split each group further into two subgroups, one receiving the material in an envelope with a printed teaser, the other in a blank envelope. Unfortunately, all envelopes were sent out as blank envelopes, so that we did not follow up on this additional intervention. The questionnaire comprised 14 pages and 47 items. Participants could opt to take part in a lottery and win an Amazon coupon (125x50€). We contacted our sample twice via post. Our primary outcome was the response rate in each group. Additional analyses are currently performed.
Results: From 9,990 persons contacted, 193 invitations were returned as undeliverable and were excluded. We received 1,341 responses to our survey. There were 679/4,890 (13.9%) responses in the IG and 662/4,907 (13.5%) in the CG with an odds ratio of 1.03 (95% confidence interval: 0.94; 1.16).
Conclusion: The present results do not show any difference in the recruitment rates. Our study does not confirm the results of previous studies. In contrast to previous studies, we did not rate the attractiveness of our photographs upfront. The greater length of our questionnaire compared to literature examples may have affected the results.
Competing interests: The authors declare that there are no conflicts of interests.
