Bland and Altman plots for the relation between subdomains of the SGRQ and CCQ. SGRQ = St George’s Respiratory Questionnaire, CCQ = Clinical COPD Questionnaire. CCQ scores by 17.67(adjCCQ). Right Y ax shows the original CCQ scale. Orange line is the regression line. Dashed lines represent the 95% confidence interval. Straight line represents the bias.