Fig. 1

a VLAD for ten simulated surgeons (black lines) performing 200 cases with actual mortality equal to the population risk level of 5 %. The blue lines are 95 % control limits set for 10,000 similar plots. b 10,000 simulations of a VLAD for a surgeon with an actual mortality rate of 2 % (red lines, 200 shown) with a population risk level of 1 % (black lines, 200 shown). The mean is the thick black line and blue lines are 95 % control limits. c 10,000 simulations of a VLAD for a surgeon performing 200 cases with an actual mortality rate equal to the population risk level of 10 % for 94 cases but then having 6 deaths in a row before resuming their initial risk (green lines, 200 shown). The black lines (200 shown) are the population level risk of 10 %, the mean is the thick black line and blue lines are 95 % control limits. d 10,000 simulations of a VLAD for a surgeon performing 200 cases with an actual mortality rate equal to the population risk level of 10 % for 94 cases but then changing to an increased actual risk level of 12.5 % (yellow lines, 200 shown). The black lines (200 shown) are the population level risk of 10 %, the mean is the thick black line and blue lines are 95 % control limits. Plots available from: http://www.datasurg.net/vlad