Given the first two columns of the following data set:
Group Height GrpMean Dog 55 55.66666667 Dog 65 55.66666667 Dog 47 55.66666667 Cat 31 29.75 Cat 28 29.75 Cat 25 29.75 Cat 35 29.75 Mouse 12 12.5 Mouse 13 12.5
Is there an easy way to generate the third column (Means for each group)? I realize I can make a "summary table" to generate the requested means (or about a half dozen other methods), but how do I get these means back into the original table, so I can use them for additional calculations? Note that my actual dataset consists of thousands of "Groups" and may not necessarily be sorted nicely as above.