Minitab first calculates the sample ranges from each set of measurements taken by an operator on a part. Then, Minitab uses the sample ranges to calculate the average range for repeatability.
Minitab calculates the variance for reproducibility from the range of the averages of all measurements for each operator. Reproducibility, in this case, is the same as the variance component for operator. Minitab calculates the variance for parts from the range of the averages of all measurements for each part.
All ranges are divided by the appropriate d2 factor.