Standard Deviation

[AlamedaMike]

Standard Deviation is an important statistic to a limit hold'em player. I think that I might be calculating it wrong in my Excel spreed sheet and maybe some one can help me out here.

Statking will calculate the STDEV for you if you provide the hours played and the $ won for each session.

For instance paired numbers (won/hours=rate)

160/2.5=64
40/4.25=9
185/2.75=67
160/3.25=49
-400/3.0=-133
150/1.5=100
145/6.0=24
190/1.75=109

Statking generates STDEV 115.94 $/hr. and WIN RATE 25.20 $/hr.

Now in Excel I calculate win rate per session and calculate stdev of the range of win rates and that is $76.36 and the win rate is $25.20. The STDEV do not agree?

Does anyone know what I am doing wrong here? Which is correct?

Here is a cool web site

I'm not sure how Statking caculates the STDEV - those numbers above geneate a $41 mean which is not my hourly rate for all the hours.

[loyo1]

AlamedaMike, too tired to track down the formula for calculating SD and my calculator. But here are is a shortcut:

Try CheckYourBets. Free online service---just input session and game info, and it kicks out SD (and other stats) for you. Very useful for tracking live play (or for non-PT supported online sites.)

Oh, you do have to register and set up an account.

[Shake_N_Bake]

Are you using the standard deviation function within Excel or are you supplying your own equation?

[AlamedaMike]

[AlamedaMike]

[AlamedaMike]

I went to the source which is the chapter on 'Computing Standard Deviation' in Gambling Theory and Other Topics by Mason Malmuth.

The formula is different than what is used by Excel. I am sure if I feed the same numbers into his formula then the Statking STDEV will match.

it is an easy formula to enter into an excel spreadsheet.

(The only reason that I bring this up is that I use a pocket PC to record my time at the card room and I want the stdev to match what I enter into Statking - solution is to have a Statking version for my Treo 700sp).

Thanks - subject closed.

Exactamondo ! I do not exactly how it works that way but it matches and that is all I care about at this point.

=SQRT(((1/COUNT(L1:L9)*L11))-((B11*B11)/COUNT(L1:L9)*D11))

If I could repeat my session results for this month for every month I would be in hog Heaven.

bb/hr = 2.2 and stdev/bb=18.34