Abstract
The properties of Cpmk in the presence of asymmetric specification limits are discussed. It is shown that Cpmk tends to zero as the process variation increases and vice versa. Furthermore, if the process variation is small, Cpmk has its maximum near the target value but the maximum moves towards the specification midpoint as the variation increases. This may be a desirable property because for large variation the percentage of items inside the specification limits is larger if the process mean is equal to the specification midpoint than if it is equal to the target value. Considering Cpmk as a mixture of Cpk and Cpm, Cpmk behaves more like Cpm if the process variation is small, whereas Cpmk behaves more like Cpk if the process variation is large. Attention is drawn to the fact that for small process variations there is a shoulder in the graph of Cpmk when the process mean is equal to the specification midpoint.
Additional information
Notes on contributors
Jutta Jessenberger
Ms. Jessenberger is an external member of the Department of Statistics. Her email address is [email protected].
Claus Weihs
Dr. Weihs is a Professor in the Department of Statistics.