Missing Values

An observation read from a DATA= or HISTORY= data set is not analyzed if the value of the subgroup variable is missing. For a particular process variable, an observation read from a DATA= data set is not analyzed if the value of the process variable is missing. Missing values of process variables generally lead to unequal subgroup sample sizes. For a particular process variable, an observation read from a HISTORY= data set is not analyzed if the values of any of the corresponding summary variables are missing.