Plotting basic control charts: tutorial notes for healthcare practitioners
- 1Department of Public Health and Epidemiology, University of Birmingham, Birmingham, UK
- 2Prism Europe Consultancy Ltd, Isle of Barra, Outer Hebrides, UK
- 3Department of Statistics, Virginia Polytechnic Institute and State University, USA
- M A Mohammed, Department of Public Health and Epidemiology, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK;
- Accepted 18 September 2007
There is considerable interest in the use of statistical process control (SPC) in healthcare. Although SPC is part of an overall philosophy of continual improvement, the implementation of SPC usually requires the production of control charts. However, as SPC is relatively new to healthcare practitioners and is not routinely featured in medical statistics texts/courses, there is a need to explain the issues involved in the selection and construction of control charts in practice. Following a brief overview of SPC in healthcare and preliminary issues, we use a tutorial-based approach to illustrate the selection and construction of four commonly used control charts (xmr-chart, p-chart, u-chart, c-chart) using examples from healthcare. For each control chart, the raw data, the relevant formulae and their use and interpretation of the final SPC chart are provided together with a notes section highlighting important issues for the SPC practitioner. Some more advanced topics are also mentioned with suggestions for further reading.