Examining the content validity of the WHOQOL-BREF from respondents' perspective by quantitative methods

Content validity, the extent to which a measurement reflects the specific intended domain of content, is a basic type of validity for a valid measurement. It was usually examined qualitatively and relied on experts' subjective judgments, not on respondents' responses. Therefore, the purpose of this study was to introduce and demonstrate how to use quantitative methods to examine the content validity for a certain measurement from respondents' viewpoint with quantitative methods. In the current study, content validity of the WHOQOL-BREF was examined with quantitative methods among 102 undergraduate students and 128 community adults. They were asked to rate the appropriateness of each item with the four domains of the WHOQOL-BREF respectively and also asked to sort the items into the four domains. Then, three quantitative methods on examining content validity were applied to analyze the rating and sorting data, including (1) proportion of substantive agreement, (2) substantive validity, and (3) ANOVA approach. These results were used to compare with the original content structure of the WHOQOL-BREF, to see if the original structure is consistent with the structure of subjects' judgments. The results showed that the content structure gained from appropriateness rating and item sorting was not totally consistent with the original content structure of the WHOQOL-BREF. Among 24 items, 12 items did not have adequate content validity. More discussion on these items and the issue of content validity were further provided.