What robust methods are common for Process Capability Indices for Non-Nornal distributions?
In Europe, we found it common to use Cpkn as a non-normal Cpk metric, where mean was replaced with median, and stdev was replaced with IQR/1.35. For some "regulatory" or "customer" reports, this seems to be accepted rather than the usual "torture the data until it says its normal" approach with transformations. Does anyone have similar experience or better ideas? (Note: any use of capabilit...