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Obtaining a high response rate is important to reduce selection bias. Some strategies, including prenotification, monetary incentives and shorter questionnaires, may increase response rates, whereas other strategies have no or unclear effects.1 We determined whether the estimated completion time and/or an unconditional gift certificate affect questionnaire response.
Pregnant women participating in the PRIDE Study were asked to fill out a postal food frequency questionnaire (FFQ) after completing the web-based baseline questionnaire.2 We employed three strategies to increase response rates in succession: (1) underestimation of completion time (10–15 min) without offering incentives, (2) underestimation of completion time with an unconditional €5 gift certificate for an online store and (3) correctly estimated completion time (20–30 min) with …
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Contributors MMHJvG was the lead author, responsible for study design, data collection, statistical analysis, data interpretation and preparation of the draft manuscript. PMG was responsible for study design, data collection, data interpretation and critically reviewed the manuscript. JHMdV was responsible for study design, data interpretation and critically reviewed the manuscript. NR designed the study, interpreted the results and critically reviewed the manuscript. All authors have read and approved the final manuscript.
Funding The PRIDE Study is supported by grants from the Netherlands Organisation for Health Research and Development (ZonMw; grant numbers 36011020 and 836012001).
Competing interests None declared.
Patient consent Obtained.
Ethics approval Regional Committee on Research involving Human Subjects.
Provenance and peer review Not commissioned; internally peer reviewed.
Data sharing statement Additional information, including sharing of PRIDE Study data, is available on request from the corresponding author (Marleen.vanGelder@radboudumc.nl).
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