In Excel you have the daily prices of all the stocks in the S&P 500 for 3 years; and the index itself.
Using all the data how might you determine which stocks had company specific movement during the 3 year period?
The simplest thing I can think of is to regress each stock against the index and then filter down to those with r-squared closest to
0. Another option is to use the correlation and filtering for those closest to
-1, but negative beta isn't necessarily company specific movement.
I'm trying to make this first iteration as simple as possible and easily visible using Excel. Is there a better approach?