Figure 1
From: Assessing regression to the mean effects in health care initiatives
Actual data illustrating the regression to the mean phenomenon in Coronary Artery Disease (CAD), Congestive Heart Failure (CHF), and Chronic Obstructive Pulmonary Disease (COPD). Quintile I is the lowest cost group and V the highest. All individuals were continuously enrolled during the 2-year period. The diagonal line represents perfect correlation between the first and second year costs, which can only be achieved in the complete absence of variability between measurements and no measurement error.