C_plog: A Capability Index for Non-Normal Processes

摘要

A new capability index C_plog has been found suitable as an index of process capability for processes that produce non-negative characteristics with one upper specification. Based on the lognormal model for process distribution, the C_plog appears to perform well where the C_p or C_pk performs poorly. The actual percentage of out-of-spec values in large samples is used to judge and compare the performance of the indices.