Application of Statistical Process Control to Physician‐specific Emergency Department Patient Satisfaction Scores: A Novel Use of the Funnel Plot
Authors: Griffen David , Callahan Charles D. , Markwell Stephen , de la Cruz Jonathan , Milbrandt Joseph C. , Harvey Timothy 
Published: March 2012

Objectives:  Emergency department (ED) patient satisfaction remains a high priority for many hospitals. Patient surveys are a common tool for measuring patient satisfaction, and process improvement efforts are aimed at improving patient satisfaction scores. In some institutions, patient satisfaction scores can be calculated for each emergency physician (EP). ED leaders are faced with the task of interpreting individual as well as group physician scores to identify opportunities for improvement. Analysis of these data can be challenging because of the relatively small numbers of returned surveys assignable to a single physician, variable numbers of surveys returned for each physician and high standard deviations (SDs) for individual physician scores. The objective was to apply statistical process control methodology to analyze individual as well as group physician patient satisfaction scores. The novel use of funnel plots to interpret individual physician patient satisfaction scores, track individual physician scores over two successive 8‐month periods, and monitor physician group performance is demonstrated.

Methods:  Patient satisfaction with physicians was measured using Press Ganey surveys for a 65,000‐volume ED over two successive 8‐month periods. Using funnel plots, individual physician patient satisfaction scores were plotted against the number of surveys completed for each physician for each 8‐month period. Ninety‐fifth and 99th percentile control limits were displayed on the funnel plots to illustrate individual physician patient satisfaction scores that are within, versus those that are outside of, expected random variation. Control limits were calculated using mean patient satisfaction scores and SDs for the entire group of physicians. Additional funnel plots were constructed to demonstrate changes in individual physicians’ patient satisfaction scores as a function of increasing numbers of returned surveys and to illustrate changes in the group’s patient satisfaction scores between the first and second 8‐month intervals after the institution of process improvement efforts aimed at improving patient satisfaction.

Results:  For the first 8‐month period, 34,632 patients were evaluated in and discharged from the ED, with 581 surveys returned for 21 physicians. The mean (±SD) overall group physician patient satisfaction score was 81.8 (±24.7). Returned surveys per physician ranged from 2 to 58. For the second period, 34,858 patients were evaluated and discharged from the ED, with 670 patient satisfaction surveys returned for 20 physicians. The mean (±SD) overall physician score for all surveys returned during the second period was 85.0 (±22.2). Returned surveys per physician ranged from 8 to 65.

Conclusions:  The application of statistical control methodology using funnel plots as a means of analyzing ED group and physician patient satisfaction scores was possible. The authors believe that using funnel plots to analyze scores graphically can rapidly help determine the significance of individual physician patient satisfaction scores. In addition, serial funnel plots may prove to be useful as a means of measuring changes in patient satisfaction, particularly in response to quality improvement interventions.