The use of control charts to improve healthcare quality.

Control charts are a basic tool for understanding variation in all healthcare processes. Control chart limits are not standards; rather, they divided variation into special and common cause, each of which requires a different management response. Each type of data--variables, count defect, or defectives data--requires a different type of chart (e.g., X bar and R, X bar and S; C or U; P or NP). Individual observations where events are infrequent can be charted on an individual's chart with moving range limits or by several alternative methods discussed in this article.