A2 measures the area between the fitted line (which is based on the chosen distribution) and the nonparametric step function (which is based on the plot points). The statistic is a squared distance that is weighted more heavily in the tails of the distribution. A small Anderson-Darling value indicates that the distribution fits the data better.
The Anderson-Darling normality test is defined as:
H0: The data follow a normal distribution
H1: The data do not follow a normal distribution
|F(Yi)||, which is the cumulative distribution function of the standard normal distribution|