VOLUME 53 | NUMBER 2 | APRIL 2015
Combining InternetBased and Postal Survey Methods in a Survey among Gynecologists: Results of a Randomized Trial
Objective: To assess whether a combination of Internetbased and postal survey methods (mixedmode) compared to postalonly survey methods (postalonly) leads to improved response rates in a physician survey, and to compare the cost implications of the different recruitment strategies.
Data Sources/Study Setting: All primary care gynecologists in Bremen and Lower Saxony, Germany, were invited to participate in a crosssectional survey from January to July 2014.
Study Design: The sample was divided into two strata (A; B) depending on availability of an email address. Within each stratum, potential participants were randomly assigned to mixedmode or postalonly group.
Principal Findings: In Stratum A, the mixedmode group had a lower response rate compared to the postalonly group (12.5 vs. 20.2 percent; RR = 0.61, 95 percent CI: 0.44–0.87). In stratum B, no significant differences were found (15.6 vs. 16.2 percent; RR = 0.95, 95 percent CI: 0.62–1.44). Total costs (in €) per valid questionnaire returned (Stratum A: 399.72 vs. 248.85; Stratum B: 496.37 vs. 455.15) and per percentage point of response (Stratum A: 1,379.02 vs. 861.02; Stratum B 1,116.82 vs. 1,024.09) were higher, whereas variable costs were lower in mixedmode compared to the respective postalonly groups (Stratum A cost ratio: 0.47, Stratum B cost ratio: 0.71).
Conclusions: In this study, primary care gynecologists were more likely to participate by traditional postalonly than by mixedmode survey methods that first offered an Internet option. However, the lower response rate for the mixedmode method may be partly due to the older age structure of the responding gynecologists. Variable costs per returned questionnaire were substantially lower in mixedmode groups and indicate the potential for cost savings if the sample population is sufficiently large.
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