Objective: To compare three different approaches for consent in postal questionnaire in terms of response rate, time consumption, and cost-efficiency, and to collect a demographic questionnaire for dropout analyses.
Study design and setting: Population survey in Sweden. Mothers and fathers (n=600) of three hundred 3-year olds were divided into three groups. One group was asked to Actively Agree to participate in a cover letter and send consent back to receive the main questionnaire. The second group received the cover letter, the consent, and the main questionnaire in the initial mailings, Direct Delivery. The third group received the cover letter and consent form in which they were asked to Actively Decline participation within 7 days if they did not want to participate. Otherwise, they were sent the main questionnaire. All parents were asked to fill in a demographic questionnaire regardless of whether they wanted to complete the main questionnaire.
Results: The highest response rate was in the Actively Decline mode. The cost-efficiency for this approach was 1.52 compared with Direct Delivery and 1.29 compared with Actively Agree.
Conclusion: Researchers can improve the response rate, time consumption, and cost-efficiency and obtain a demographic questionnaire for dropout analysis by using the Actively Decline approach for postal questionnaires.
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