Figure 1.

Bivariate scatterplots of the first vs second measurement and of the difference between measurements vs average value of measurements conceming the BDI-21 score. The points of the test-retest plot are very close to the regression line (which is a dichotomous) and the points of the difference vs. average are within the 2 SD from the mean difference (the scatterplots are based on test-retest data from 20 subjects, however some points overlap)