Standard Deviation

Standard deviation quantifies the amount of variation in gambling results. In practical terms, it tells you how much your actual results are likely to differ from the expected value.

For a series of bets, about 68% of outcomes will fall within one standard deviation of the expected value, and about 95% within two standard deviations. The higher the standard deviation, the wider the range of likely outcomes.

This concept is essential for understanding whether your results reflect skill or luck. If your actual results fall within the expected range of variance, you can't conclude much. Only when results consistently fall outside the expected range can you identify a real edge — or a real problem with your strategy.