-In this mode, you must also use the @cmd{/VARIABLES} subcommand to
-tell PSPP the dependent variables you wish to test.
+If the parentheses are omitted and no values are given, the default values
+of 1.0 and 2.0 are assumed.
+
+If the independent variable is numeric,
+it is acceptable to specify only one value inside the parentheses.
+If you do this, cases where the independent variable is
+less than or equal to this value belong to the first group, and cases
+greater than this value belong to the second group.
+When using this form of the @cmd{GROUPS} subcommand, missing values in
+the independent variable are excluded on a listwise basis, regardless
+of whether @cmd{/MISSING=LISTWISE} was specified.
+