Agreement between web-based and paper versions of a socio-demographic questionnaire in the NutriNet-Santé study
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Web-based studies nowadays raise a major interest as they can improve all steps involved in observational studies. Our objective was to compare the web-based version of the NutriNet-Santé self-administered socio-demographic and economic questionnaire with the traditional paper version.
Both versions of the questionnaire were sent to 170 volunteers and filled in by 147 of them (either paper first, n = 76, or web-based first, n = 71). Agreement between versions was assessed by intraclass correlations (ICC) and kappas.
Agreement between both versions was high, with ICC and kappas ranging between 0.81–1.00 and 0.76–1.00, respectively, similarly across groups of administration order, age, gender and self-estimated web knowledge in general. The web-based version was the one preferred by 93.7% of the subjects and enabled to avoid 553 missing values (2.00% of the total entries), 24 inconsistent data (0.09%), 8 aberrant data (0.03%), 472 data entry errors (0.85%) and to save 2,800 € (US $4,072) when sent to 170 subjects.
The web-based socio-demographic and economic questionnaire provided information of similar-to-superior quality compared to the traditional paper version, with substantial logistic and cost advantages.