Your Personal Standard Deviation?

The concept and formula of computing one's personal StDv is provided here by Malmuth for poker pros, it is perhaps valid for BJ as well? I have suggested to several BJ pros that this method, occaissionally re-calc'd every 30-70 sessions, could provide a counter with an ideal addt'l tool... Mr.Mayor, what is YOUR personal StDv? zg


Computing Your Standard Deviation
by Mason Malmuth (Archive copy)

Everyone plays poker differently, and no two poker games are identical. This means that no two skilled or unskilled players will have identical results. Specifically, no two players will have exactly the same win (or loss) rate, and no two players will have exactly the same standard deviation.

In the essay titled "How Much Do You Need?" standard deviations for different poker games were given based on one expert's playing results. You, the skilled player, should estimate your own standard deviation for the particular game or games that you play. In addition, this estimation should be updated every so often to account for natural changes - such as new players - that the games go through.

The easiest way I know to estimate your standard deviation is to use the following formula. This formula was derived by Mark Weitzman and is the maximum likelihood approximation for the standard deviation.

Complete article and formula here - (Archive copy)

The Mayor

Well-Known Member
You asked what my personal Std. Dev. is. The basic problem is that Standard Deviation is based around individual samples of some fixed size. If you take my win/loss per day, well some days I play 30 minutes, other 12 hours. If you want to know my win/loss per hour, I don't keep records of that. It is simply not possible to give a uniform value for the sessions or the period over which a sample is taken, and therefore it does not make sense to talk about it on an individual basis. In addition, I have changed counting systems, bet schemes, and play a variety of games. Any one of these will have an effect on my STD DEV. that would need to be measured separately.

I am dubious :cool:

In Blackjack, STD DEV does not depend on style of play, the way it does in poker. Poker players can be "loose" (read that -- high STD DEV) or "tight" (that is, a low STD-DEV). They can be passive or agressive. Tight agressive is the winning style, as I am sure you know.

In blackjack, if you play correctly your STD DEV will be fairly close to the predicted value in the long run.

My own journal and tracking always includes time-played, so my StDv can be based on a re-calc for every 30-70 sessions. Such tracking makes the BJgame more personal - I'd recommend that every counter know his StDv, just we know our personal winrate. A valuable, if only to further reinforce the risk-flux-reality of the undertaking. zg