The impact of varying patient populations on the in-control performance of the risk-adjusted CUSUM chart

Int J Qual Health Care. 2015 Feb;27(1):31-6. doi: 10.1093/intqhc/mzu092. Epub 2014 Dec 8.


Objective: This research is designed to examine the impact of varying patient population distributions on the in-control performance of the risk-adjusted Bernoulli CUSUM chart.

Design: The in-control performance of the chart is compared based on sampling the Parsonnet scores with replacement from five realistic subsets of a given distribution.

Settings: Five patient mixes with different Parsonnet score distributions are created from a real patient population.

Main outcome measures: The outcome measures for this research are the in-control average run lengths (ARLs) given varying patient populations.

Results: Our simulation results show that the in-control ARLs of the risk-adjusted Bernoulli CUSUM chart with fixed control limits and a given risk-adjustment equation vary significantly for different patient population distributions, and the in-control ARLs decrease as the mean of the Parsonnet scores increases.

Conclusions: The simulation results imply that the control limits should vary based on the particular patient population of interest in order to control the in-control performance of the risk-adjusted Bernoulli CUSUM method.

Keywords: Parsonnet score; average run length (ARL); heterogeneous population distributions; in-control performance; risk-adjusted CUSUM; statistical process control.

Publication types

  • Comparative Study

MeSH terms

  • Age Factors
  • Bias
  • Computer Simulation
  • Health Status
  • Humans
  • Models, Statistical
  • Quality of Health Care
  • Risk Adjustment / methods*
  • Risk Adjustment / standards*
  • Risk Factors