Well, transitive "average out" in a numerical sense does seem to exist. I've cited dictionary entries (Cambridge, Macmilllan). Here's another (Longman):
"
average something ↔ out to calculate the average of something
I averaged out the total increase at about 10%."
https://www.ldoceonline.com/dictionary/average-outAnd here's another example from Cambridge:
"This is the equivalent of 37,000 families paying nearly £3 billion, around £80,000 each if you average it out"
And Oxford gives another, under transitive "average":
"their earnings, averaged out over the month, were only $62 a week"
https://en.oxforddictionaries.com/definition/us/average#aver...Collins Cobuild also gives it:
"If a set of numbers average out to a particular figure or
if you average them out to that figure, their average is calculated to be that figure.
Averaging it out between us there's less than £10 a month each to live on."
My point was that I found it in these British dictionaries, but not in American ones, so I was wondering whether, to the extent that it exists at all, it is British rather than American. In any case, I think it's unusual, and nothing is lost if "out" is omitted.
peer agreement (net): +2