Using calculated field and inserting results into a formula.

You can have conditional calculations that check column A for specific values, like these array-entered formulas (enter with ctrl-shift-Enter): they will return the correct value even as the data set changes.

=MEDIAN(IF(DataAll!$A$2:$A$100000="UM_Ann-Arbor",DataAll!$AA$2:$AA$100000))
=MEDIAN(IF(DataAll!$A$2:$A$100000="UM_Dearborn",DataAll!$AA$2:$AA$100000))
=MEDIAN(IF(DataAll!$A$2:$A$100000="UM_Flint",DataAll!$AA$2:$AA$100000))

If you have more than 100,000 rows, just change each of the 100000s to something higher, like 200,000

=MEDIAN(IF(DataAll!$A$2:$A$200000="UM_Ann-Arbor",DataAll!$AA$2:$AA$200000))
=MEDIAN(IF(DataAll!$A$2:$A$200000="UM_Dearborn",DataAll!$AA$2:$AA$200000))
=MEDIAN(IF(DataAll!$A$2:$A$200000="UM_Flint",DataAll!$AA$2:$AA$200000))

Using too many rows will slow down your calculation, so don't reference entire columns - just enough rows that covers your entire expected data set.