Convergent and discriminant validity of the WHOQOL-BREF using a multitrait-multimethod approach

The WHOQOL-BREF is a commonly used questionnaire in quality of life research. Previous research has shown that the four domains of the WHOQOL-BREF (physical health, psychological health, social relationships, and environmental health) are highly related. Whether these high correlations reflected the true relations across the domains or the influence of common method effect; however, is still unknown. This study examines the convergent and discriminant validity of the four domains of the WHOQOL-BREF by using the multitrait-multimethod (MTMM) approach to control the method effect. Two different samples, with a total of 186 and 201 adults, respectively, were used in the present study. Each participant filled out the WHOQOL-BREF questionnaires using four different scaling methods (Likert-type scale, visual analogue scale, pie scale, and partner rating). The covariance matrix of the MTMM result was analyzed with confirmatory factor analysis modeling. Two models were applied, including the correlated traits-correlated uniqueness (CTCU) model and the uncorrelated traits-correlated uniqueness (UTCU) model. Results showed that the CTCU model fit the data better than did the UTCU model, suggesting that the variables tapping the four domains of the WHOQOL-BREF have excellent convergent validity; the four domains have moderate correlations, indicating that the four domains are related but not identical.