Figure 1

Example of a funnel plot visually exploring the issue of variability in all-cause in-hospital mortality rate for fractured neck of femur (NOF) between providers. 37.5% of hospitals lay outside the 95% (green lines) confidence intervals (green) and 18.1% of hospitals lay outside the 99.8% (red lines) confidence intervals. Further statistical analysis determined whether the probability that the number of hospitals outside the confidence intervals was significant (both p < 0.0001).