The process of analyzing gage variability is often highly structured, involving an examination of the gages themselves for sensitivity to temperature changes, magnetic fields, and other factors. These are the easy ones. The second area of variability has its source in gage operators themselves, who may have different levels of training, experience, fatigue, and even attitude.
Collecting data offers clues to sources of variability. But when this disciplined analysis fails to uncover real reasons for variability, it may be time for the Sherlock Holmes of variability to look at operational definitions—often the most overlooked consideration when evaluating variation among measurement devices.