The Anderson-Darling statistic is a measure of how far the plot points fall from the fitted line in a probability plot. The statistic is a weighted squared distance from the plot points to the fitted line with larger weights in the tails of the distribution. Minitab uses an adjusted Anderson-Darling statistic, because the statistic changes when a different plot point method is used.
Minitab provides an Anderson-Darling statistic for the maximum likelihood and least squares estimation methods.
number of plotted points
fitted estimate of the cumulative distribution function for the ith point
the point plotted for the ith data point
Pearson correlation coefficient
For least squares estimation, Minitab calculates a Pearson correlation coefficient. If the distribution fits the data well, then the plot points on a probability plot will fall on a straight line. The correlation, usually signified by r (rho), measures the strength of the linear relationship between the X and Y variables on a probability plot.