Statistical Process Control (SPC)

Statistical Process Control (SPC) is a quality management technique that applies statistical methods to monitor and control processes. Its goal is to distinguish between common cause variation (natural, inherent to the process) and special cause variation (assignable, due to external or unusual factors). Control charts are the primary SPC tool, plotting process data against statistically determined limits. A process is considered stable when only common cause variation is present. SPC improves productivity by reducing variation, detecting problems early, and preventing defects. Western Electric rules and Nelson rules provide criteria for identifying special causes. SPC is widely used in manufacturing, service industries, and healthcare to ensure consistent quality.

Governing FormulaControl limits: UCL = μ + 3σ LCL = μ - 3σ Centerline = μ Where μ = process mean, σ = standard deviation

Knowledge Check

10 Questions

1.What is the main purpose of SPC?

2.In SPC, common cause variation is also called:

3.What is the typical number of standard deviations used for control limits?

4.When is a process considered 'in control'?

5.Which of the following indicates a special cause of variation?

6.Which rule set is commonly used to detect special causes in SPC?

7.SPC is based on the principle that:

8.What is a 'run' in SPC?

9.What does the centerline in a control chart represent?

10.Which of the following is NOT a benefit of SPC?