Question for Quantopian team:
Based on that post by Q management https://www.quantopian.com/posts/june-contest-rules-update-its-all-about-that-beta-star
it looks like proper Beta calculation for portfolio is based on last 252 day window.
However, Beta value that we see during backtests is based on the full portfolio lifetime.
So, which one is the right one? Probably, the one you use for contest, Right?
If so, why this is so difficult to correct backtests code?
If internaly inside my algo I'm calculating Beta for last 252 days, should I trust the one I've calculated? If I show it through record() would Q beleive me?