Constructing powerful control charts

Control charts are intended to tell a story about whether or not a process is stable, improving, or deteriorating. Effective storytelling requires more than correctly following the rules for choosing the best control chart and applying the tests for a special cause. The story will be told more effectively when control charts include all the information needed to convey the key messages and exclude information that distracts from the storyline. This article presents some graphical guidelines for making control charts tell their stories more forcefully.