How to use the Calculator
Simply put in your long-term ROI into "Expected ROI" and the ROI you've experienced over the sample into "Observed ROI." Enter your sample as a # of games.Over any randomly selected sample of games, the chance that you are +/- 1 standard deviation is 68.2%. The chance that you are +/- 2 standard deviations is 95%. The chance that you are +/- 3 standard deviations is 99.7%.
Probably the most accurate, mathematically, use of this calculator is to select a sample where you ran badly and say "what is the chance that I run this badly over my next X games." If you are more than two standard deviations away from the mean, the chance that you run this badly again over your next set of games is very, very unlikely.
Caveats & Warnings
- If your ROI has changed during the sample, for example, running bad has caused you to play worse, then the calculator will over-estimate your standard deviation
- Due to rounding errors, the calculator can be off by +/- a fraction of a standard deviation.
- The calculator only work for heads up sit and gos where the rake is 5% of the buyin. It does not consider winnings due to rakeback.
- If you are selecting a sample over which you ran your worst, this is not a "randomly selected" sample and will give skewed results.
- What is the chance of losing X buyins? If you play an infinite number of games, the chance of losing X buyins is always "1" -- you will eventually run infinitely bad. As such, you can't ask "what's the chance of losing X buyins," because the question is mathematically absurd.
