Evaluate Control Procedures by Examining Errors in Process Adjustment

Abstract

A procedure is proposed for use in evaluating the effect of various control chart procedures. This consists of breaking the power curve associated with a particular control chart technique into four component parts. These are:

• γ₁ — probability of undercorrecting

• γ₂ — probability of overcorrecting, but still improving

• γ₃ — probability of overcorrecting in excess

• γ₄ — probability of adjusting in the wrong direction

These components will be illustrated for a number of situations including Shewhart charts, partial correction procedures, geometrically weighted moving averages, cumulative sums, and an example which includes variability associated with the adjustments and variability in the process before adjustment.

• Control Charts
• Control Limits
• Cumulative Sum Chart
• Moving Average Chart Error Probabilities
• Process Adjustment Errors

Additional information

Notes on contributors

J. Edward Jackson

Dr. J. Edward Jackson is a staff consultant with the Eastman Kodak Company. He is a fellow of ASQC.