Fig. 2
From: Comparison and concordance of health-related quality of life tests among substance users
Common person equating: HRQOLDA test and WHOQOL-BREF Questionnaire (a), HRQOLDA test and DUQOL scale (b), and WHOQOL-BREF Questionnaire and DUQOL scale (c). Dots represent persons. The black line represents the empirical regression line. The dotted lines represent the estimates’ 95 % CI