The Anderson-Darling normality test can help you determine whether the data follow a normal distribution. The A statistic that the test provides is not very informative by itself, but it is used to determine the p-value. The p-value ranges from 0 to 1, and indicates how likely it is that your data follow a normal distribution.

First, you need to decide how low the p-value must be for you to conclude that the data are not normal. (A commonly chosen value is 0.1.) Then, if the p-value is lower than your criterion, you must conclude that the data do not follow a normal distribution. Otherwise, there is not enough evidence to conclude that the data do not follow a normal distribution.

The Anderson-Darling normality test statistics are located in the upper right corner of the Graphical Summary.

The value of A-Squared for the precipitation data is 0.99, and the associated p-value is 0.008. Assuming you chose 0.1 as the level of significance, you must conclude that the data do not follow a normal distribution, because 0.008 is lower than 0.1.