Measuring health care quality. How do you know your care has improved?

Statistical process control (SPC) was developed in the 1920s as a way of detecting defects in manufacturing processes. During the past decade, SPC has been adopted by service industries and is increasingly being employed by health care organizations. The methodology involves the construction of a control chart to detect variation within processes. Variation is neither good nor bad in itself; therefore, the impact of variation must be interpreted within the context of expected outcomes, acceptable limits, and the process itself. In this article, the concept of statistical process control is explained, and examples are provided to illustrate how SPC can be applied in a clinical setting.