Assessing Process Capability in the Presence of Systematic Assignable Cause

Abstract

A process must be considered free from variation due to assignable cause before its capability can be determined. In those situations where variation due to an assignable cause occurs and is tolerated, process capability cannot currently be assessed. By allowing the process capability to be considered dynamic, a procedure for assessing capability is proposed and an estimator developed for those situations where a systematic assignable cause occurs. Some statistical properties of the estimator are examined and a technique for managing a process exhibiting a systematic assignable cause is discussed. Examples from a particular class of systematic assignable cause known as tool wear are included.

• Process Capability
• Process Capability Index
• Systematic Assignable Cause
• Tool Wear

Additional information

Notes on contributors

Fred A. Spiring

Dr. Spiring is an Assistant Professor in the Department of Statistics. He is a Member of ASQC.