Process capability and incapability indices are numerical tools that evaluate the ability of a process in conformance with the required specifications. The process incapability index C\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"pp, introduced by Chen -1998-, provides numerical measures on process precision, accuracy and performance. This paper considers the effect of measurement error, usually from measuring instruments, on C\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"pp and investigates the statistical properties of the estimated index. The results indicate that incapability index based on the measurement error has an important role in detecting process performance and ignoring it causes the process performance to be underestimated.

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