Fig. 2. Comparison of propensity scores for the use of catecholamines by group and quartiles. The figure contains eight box plots. The lower and upper ends of each box denote the 25th and 75th percentiles, respectively. The solid horizontal line through each shaded box denotes the median of the distribution, and the cross denotes the mean. The vertical solid black lines (whiskers) reach out to 1.5 × the interquartile range. The circles above the whiskers denote individual extreme observations. The bars represent the number of subjects included in each quartile.