Statistics - Determining Confidence Level

SpiderWeb · Jul 30, 2009

Hey folks. I used to be great at this stuff, but it's been a few years since I've seen a statistics book. The question is this:

Handicapper Bob bets only on games with -110 lines. Bob has predicted 135 games so far with his new system, with a record of 82-53.

With what percent confidence can Bob say that his system will be AT LEAST break even? That is, with what percent confidence can Bob say that his system will win 52.38% or more of his bets?

Thanks for any help. I'm really embarrassed that I can't figure this out!

ds123 · Jul 30, 2009

I'm not a statistics master, but I'm pretty sure a confidence interval does not apply here.

Confidence interval is for, "I measured 100 random kids' IQ's and they average out to 150 with this standard deviation. What is the range of IQ's that I can be sure 95% of all kids fall into?" The thing being measured (IQ) has to have a continuous range of values, not just WIN or LOSE.

That being said, what you ARE looking for is binomial distribution calculator. Search that term on Google and you will get them. It basically asks "If the odds of a winning wager are X, what are the odds I get a winning percentage of Y over the next N number of bets. " You can specify X, Y, N into the calculator and it'll spit out a number.

I hope that helps, I'm not a stat major!

parlayallday · Jul 30, 2009

wow. thats all i can say

SpiderWeb · Jul 30, 2009

Thanks for the suggestion. It was stuck on the tip of my tongue.

I found a good calculator at http://stattrek.com/Tables/Binomial.aspx in case anybody reads this in the future. The result was a 97.9% chance that it wins at least 52.4% over time.

tommyjohn44 · Jul 30, 2009

97.9% chance of success using binomial distribution

SpiderWeb · Jul 30, 2009

parlayallday said:
wow. thats all i can say

Wow to the question? or wow to the record lol?

Over that sample size, 60% is very good but not anything spectacular. I realize that it won't stay that high, but just wanted to make sure it would stay above the "break even" mark.

If it stays at 60% for 1000 more picks I'll let you know :toast:.

Actually, no I won't. I'll be hiding in a cave in Las Vegas :dancefool