Standard deviation
A measure of how far results usually swing either side of their average.
Last updated
- What it means
- Standard deviation puts a number on spread. A small one means results sit close to the average; a large one means they land far from it in both directions.
- How it is calculated
- Over many results, about two thirds fall within one standard deviation of the average and about 95% within two.
- Worked example
- A cash player averaging +5bb per 100 hands with a standard deviation of 100bb per 100 finishes about two thirds of 100-hand stretches between −95bb and +105bb.
- Why it matters
- Tournament results have a very large standard deviation next to their average, which is why a long losing run says little about how well you played.
Try it: Variance and bankroll calculator, Cash game variance calculator
See also: Variance, Winrate confidence, Downswing, Bankroll