Fig. 3.

Bland-Altman plots, combining ratings over the three time points (n = 608). The solid horizontal line is drawn at the mean of the differences in ratings ($\overline{d}$) within dyads, thus providing an estimate of the amount of overall bias. The two dashed lines are 95% limits of agreement defined as $\overline{d}$ ± 1.96 s _d where s _d is the standard deviation of the differences corrected for clustering [29]. These lines delimit the range within which 95% of the differences lie. Scores below the zero difference line indicate that the proxy provided a higher rating than the older adult (i.e., poorer health-related quality of life), and conversely for scores above that line