- A trend chart with control limits
- Graphical representation of process performance, where data is collected at regular time sequence of production
- Valuable tool for differentiating between common cause and special cause variation
- Evaluating whether a process is or is not in a state of statistical control
- It lets the data ‘talk’ by itself & basis for data-driven decisions
A typical control chart consists of three lines :
CL: The average (measure of location) process performance when the process is in-control
UCL & LCL: The range of ‘usual’ process performance when the process is stable. Lines drawn 3 standard deviations (3 sigma) on each side of the center line.