Fig. 1

Box plot of inpatient days used, displayed as four six-month periods before and after the patients signed the PCA contract. Boxes represent the second and third quartiles, divided by the median bar. The whiskers mark an additional 1.5 interquartile range. Circles mark mild outlying observations (up to three interquartile ranges) and asterisks mark extreme outliers (outside three interquartile ranges) outside the middle quartiles