Displaying random variation in comparing hospital performance

IntroductionThe role of transparency in quality of care is becoming ever more important. Various indicators are used to assess hospital performance. Judging hospitals using rank order takes no account of disturbing factors such as random variation and case-mix differences. The purpose of this article is to compare displays for the influence of random variation on the apparent differences in the quality of care between the Dutch hospitals.MethodThe authors analysed the official 2005 data of all 97 hospitals on the following performance indicators: pressure ulcer, cerebro-vascular accident and acute myocardial infarction. The authors calculated CIs of the point estimate and the simulated CIs of the ranks with bootstrap sampling, and visualised the influence of random variation with three modern graphical techniques: forest plot, funnel plot and rank plot.ResultsStatistically significant differences between hospitals were found for nearly all performance indicators (p