As usual, first the function:
This is quite a different animal. The application of it isn't really sales, on wikipedia it even says that this applies to electricity, but I don't have those kind of figures -- it'll work just as good with my numbers. It no longer takes into account the number of items sold, so our starting table is going to look a bit different:
In our case, this is 1/12 or : 0.08.
Next, we have to take the second power of each unit price.. easy peasy.
=power([Sold at (unit price)];2)
And next, we need to add those up:
=Sum(Power([Sold at (unit price)];2))
Next, we have to multiply those and take the square-root.
=sqrt(Sum(Power([Sold at (unit price)];2))*(1/Count([Lines])))
The Quadratic mean of the unit price is 167 -- so far, that's the highest mean we got.
More averages coming up.