Comparison between web-based and paper versions of a self-administered anthropometric questionnaire
OBJECTIVES The aim was to assess the content, validity and reproducibility of web-based questionnaires, for a study on osteoporosis prevention among young British women. Twenty-two questionnaires to assess knowledge, self-efficacy, physical activity, calcium intake, health beliefs and stages of change relevant to osteoporosis prevention were identified. Nine were selected and modified to compensate for cultural differences, to suit young women, for completion on the Web. DESIGN Subjects were recruited by e-mail and asked to complete the web-based questionnaires. Subjects completed the questionnaires again, on paper and were asked to assess the content validity, at least seven days later. SETTING University of Glasgow, Scotland. SUBJECTS Sixteen female students and staff aged 19-49. RESULTS The questionnaires' reproducibility, as measured by the intraclass correlation coefficient was significant at p < 0.01 and acceptable, i.e. above 0.70 for knowledge, 0.85; for self-efficacy, 0.72; for exercise stage of change, 0.79; for exercise benefits, 0.89 and for exercise barriers, 0.82. The intraclass correlation coefficient was significant at p < 0.01 for health belief, 0.43, for weight-bearing physical activity, 0.67, for calcium barriers, 0.48, for 'others around you', 0.65, for calcium stage of change, 0.50 and for calcium intake, 0.56. The intraclass correlation coefficient was not significant for calcium benefits. CONCLUSIONS Assessing content validity was valuable in ensuring questionnaires were relevant and interpreted correctly by the sample population. Nine web-based questionnaires suitable for, and validated with, young British women are now available for use as outcome measures in studies of health education to prevent osteoporosis.