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tomcain
01-02-2004, 05:08 PM
Hello

My math is too rusty. I am trying to create a spreadsheet to calculate my BB/hr. Let me give a simple example. Assume I always played .50/1.00 tables. I keep session detail records.
Time won/lost bb/hr
1 hr +10.00 10.00
2 hr -5.00 -2.50

3 5.00 1.67 is correct

However, averaging the bb/hr column produces 3.75bb/hr, which is wrong. It only gets more complicated and farther off if I play at different size tables. Somehow I need a weighted average that also works correctly across different table sizes.

A more complicated example with different BB sizes

BB Time won/lost bb/hr
1.00 1 hr +10.00 10.00
2.00 2 hr -5.00 -1.25

3 5.00

Average of bb/hr produces 4.38

What would be the correct formula to use in a spreadsheet to get my overall bb/hr?

TIA, Tom

Bozeman
01-02-2004, 07:09 PM
Personally, I wouldn't average accross multiple limits, since the competition will change significantly.

tomcain
01-02-2004, 07:46 PM
Fair enough. However that does not answer the question. Even averaging within the same limit does not give the right answer.

Thx, tom

fluff
01-02-2004, 07:54 PM
Can't average the BB/hr column. Instead, sum your hours, sum your won/lost, then devide sum of won/lost by sum of hours. Hope that helps.

Keep separate sheets for different limits.

BruceZ
01-03-2004, 01:49 AM
Now hold on a second. Not to be rude, and I never criticize anyone for asking a basic question, but you're a computer consultant with a math and computer science degree, and you can't add your winnings and divide by hours played to get your average winnings per hour? How is that possible? /images/graemlins/confused.gif How do you compute your bowling average? I assume you're pulling our leg somehow.

Perhaps this is meant to be a parody of some other posts which appear here. I too have noticed that many people will use the excuse that their math skills are rusty, and then proceed to ask a question which requires no specialized knowlege of math, but merely an ability to think logically and have confidence in their own thinking ability.

I don't want this to discourage anyone from asking questions. I encourage everyone to ask questions no matter how basic they may be; however, if you try to answer them on your own first as best you can, you will get much more from this forum, and you might be surprised at how much math you actually can do.

tomcain
01-03-2004, 11:54 AM
Well of course i figured out the correct answer, as my post indicated. I could not reconcile, in my mind, why the average of the per session rates was so far off from the correct answer.

I thought there might be something simple I was missing.

Tom

BruceZ
01-03-2004, 01:15 PM
I thought there might be something simple I was missing.

(a + b) / (x + y) does not equal a/x + b/y


What would be the correct formula to use in a spreadsheet to get my overall bb/hr?

Excel format:
column A = session win, rows 1 to x
column B = session hours, rows 1 to x
column C = total win, rows n = 1 to x: =SUM(A$1:An)
column D = total hours, rows n = 1 to x: = SUM(B$1:Bn)
column E = total win/hr, rows n = 1 to x: =Cn/Dn

I can email you an Excel spreadsheet that does this and also computes standard deviation if you want. In exchange you can explain to me how to adjust to PBA lane patterns A-E. /images/graemlins/grin.gif

Bozeman
01-03-2004, 02:24 PM
If you must do an average of per session stats, then it is a weighted average (sum(sessionwinrate*time/totaltime)). For different limits, if you'd like your average win rate in BB/hr (though this number is essentially meaningless), you could use the same formula, as long as you express all sessionwinrates in BB.

tomcain
01-03-2004, 05:40 PM
Thank you. that makes sense.

Tom

tomcain
01-05-2004, 09:42 AM
Bruce

I already have my spreadsheet, without the std dev. I did it both ways and that was how I found the discrepancy to start with.

Interestingly enough, in bowling you can average the weekly averages and get the correct answer,
[ QUOTE ]

(a+b+c)/3 + (d+e+f)/3)/2 = ((a+b+c) + (d+e+f) )/6


[/ QUOTE ]

Unfortunately, I cannot help you in the PBA. That was a dream 30 years ago. My state scratch singles title was the height of my bowling career, at age 49. I am especially proud of it because the state tournament is open to both pros and amatuers. I got very lucky. I am a stroker from when 200 was a rare average. The shot was very demanding on wood and all the young power players died.

Tom

BruceZ
01-05-2004, 09:50 AM
Interestingly enough, in bowling you can average the weekly averages and get the correct answer

Only because you play the same number of games every week, otherwise you could not. Same as if you played the same number of hours each session in poker. Nothing mysterious about that.

I have a stroker's style too.