Standard Deviation

[GMontag]

How do you calculate the standard deviation of a weighted population? I'm trying to create a spreadsheet to track my B&M sessions. I have profit/loss and length of time data per session, but the sessions are obviously different lengths so I assume the normal formula doesn't work.

[Justin A]

Pay for and download StatKing, it will do it for you.

Or you can look in Mason's Gambling Theory and Other Topics as I believe it has a thorough explanation. If I come back to this thread when I have more time and no one has given an answer I'll relay what it says in that book, but that's unlikely since I won't have enough free time till Monday.