For the Pure Error DF, consider the multiple instances in the Big Class.jmp sample data table where more than one subject has the same value of height. In general, if there are g groups having multiple rows with identical values for each effect, the pooled DF, denoted DFp, is as follows:

ni is the number of subjects in the ith group.

For the Pure Error SS, in general, if there are g groups having multiple rows with the same x value, the pooled SS, denoted SSp, is written as follows:

where SSi is the sum of squares for the ith group corrected for its mean.

Because Pure Error is invariant to the form of the model and is the minimum possible variance, Max RSq is calculated as follows: