I'm studying for the SAS Advanced exam and one of the study questions is the following:    When attempting to minimize memory usage, the most efficient way to do group processing when using the MEANS procedure is to use: A.The BY statement. B.GROUPBY with the NOTSORTED specification. C.The CLASS statement D.Multiple WHERE statements.   I'm pretty sure the answer is A, but I'm confused about answer B. What is GROUPBY? Can it even be used with proc means?    Thanks in advance!  ... View more