Probably trivial question about dax averages, help?

[Guitarmageddon]

Hello all, really racking my brain on this one. I go in these phases where I use dax a bunch, then dont use it at all and forget simple things I already learned. So here is a pivot table of some sales data. It is simply summarizing the 52 week sales for a store number, segmented within various assortment footages (i.e. 3,4,8,12 and so on).

I am trying to do a measure that shows how far above or below the average that particular store's sales dollars are. I have tried some different iterations of calculate/filter/average x and so on and cant remember how they work together. trivial, I know.... can anyone offer some suggestions? For example, I know the average of the 3ft column is 9583 dollars, so in my brain, Id produce a value lets say for site 02301, that would be a -$7282.

Here is a snip of what the pivot output, would this help?

 

[macfuller]

Try this link. It's a bit more than you're looking for but you'll find the basic average measure you're looking for. Be sure to check the comments for a revised STDEV measure if you want to do the whole thing.