Fig. 1. Histogram of the percentage of cases that were of a procedure that occurred a specified number of times in the pooled case duration data from four medical facilities. When a patient enters and then leaves an operating room, one case  is performed. The case can include one or more surgical procedures. To obtain the histogram, the 200,401 cases were sorted by procedure. The number of times that a patient entered an operating room and underwent a specified procedure was counted. The counts were sorted in ascending order. Each bar shows the sum of the counts divided by the total number of cases. The number of cases per procedure was then plotted along the horizontal axis. These numbers are reported as a range for each bar, rather than on a logarithmic scale, to indicate clearly the values for procedures performed only once or twice (the far left bar).