Control charts were originally used in the deployment of Statistical Process Control (SPC) and later on adopted into the Six Sigma framework. Also known as Shewhart charts (after Walter A. Shewhart), these charts look into the process behavior as well as its natural (common) or special (assignable) causes of variation. Control charts set statistical control limits (upper and lower) where most of the process data are expected to fall within. By using control charts, one can identify areas of poor performance or excellence and adapt accordingly. In this article, we will go over the basics of creating a control chart, the four process states within a control chart, and the different ways that these charts can be used.
How to Create a Control Chart
The most common way to create a control chart is by entering data points into Excel and using formulas to create a chart. There are seven different types of control charts you can create depending on the amount and type of available data. More robust tools like SigmaXL or R can also be used to create control charts for both continuous and attribute data.
Identifying the Four Process States in a Control Chart
There should be four process states within a control chart: the ideal state, threshold state, brink of chaos state, and the out of control state. Each of the four process states reveals the stability and predictability of the process and helps identify, through data, whether the process is under control or is becoming increasingly prone to error. Specific rules can be applied to trends, shifts, and out of control process behavior.
Different Uses for Control Charts
Control charts are primarily used as a tool to control, monitor, and improve processes by identifying patterns that develop over time and finding areas that need improvement. Control charts have uses in a variety of contexts such as response time, budgeting, quality control, and beyond, making them a useful tool to learn regardless of the work setting.
How Adonis Can Help
Control charts are a key tool in striving for continuous improvement. Here at Adonis, we provide training in the Lean Six Sigma toolkit that will help you master utilizing control charts and other continuous improvement strategies.