Unboxed Solutions Blog The frenetic soapbox
Hit a bit of a snag creating an Avg Score measure in my cube in SSAS. I used the AverageOfChildren aggregation behavior and apparently this ignores the Date dimension because it is semiadditive. To create an [Avg Anything] measure, create a Sum measure and a Count measure, then create a calculated member as Sum / Count....or define the calculated member in your MDX statement every time.
Anyway, hope this helps someone else who runs into the same issue.