Fig. 5. Confidence intervals (90 and 95%) for average adjusted operating room utilizations obtained by using 3 months of data, while having all cases exactly the same duration: 3.75 h or 25 min. The average adjusted OR utilization is the independent variable in the computer simulations. The duration of 3.75 h matches the mean duration of cases in Figs. 1–4. The figure shows that average OR utilization can be estimated more precisely for surgeons who care for more patients each week in OR block time. Numbers of cases matters, not hours of cases.