Repeatability is the amount of variation in the measurement system that is from the gage. An attribute gage study regresses the probabilities of acceptance on the reference values to obtain repeatability.
Pre-adjusted repeatability is the repeatability that is calculated before adjusting for over-estimation. Minitab divides estimates of repeatability by the adjustment factor 1.08 to calculate the adjusted repeatability. The adjustment factor of 1.08 is given by the Automotive Industry Action Group (AIAG)1.
A low repeatability value indicates that the gage measures consistently. A high repeatability value indicates random variation, or problems such as an inadequate selection of parts or a poor gage.
Minitab uses the adjusted repeatability value in the calculation to test the null hypothesis of bias = 0.