Part III: Business & Regulation · Gambling Mathematics & Probability

62. Volatility Index (VI) — Gaming

Risk Management

In gaming mathematics, the Volatility Index is a standardized measure of a game’s payout variability, calculated as 1.96 times the standard deviation of all possible game outcomes at a one-unit bet level. The VI is used by regulators and game designers to determine how many plays are required before a game can be statistically expected to achieve its minimum required payout percentage. The formula, as specified in Pennsylvania gaming regulations, is: VI = 1.96 x Standard Deviation, where the standard deviation is the square root of the difference between aggregate variance and the square of the lowest payout percentage. Games with high volatility indexes (typically progressive jackpot slots and games with rare large prizes) require substantially more plays to converge to their theoretical RTP.

In practice

Formula: VI = 1.96 x sqrt(Aggregate Variance - (Lowest Payout %)^2). The number of plays required for regulatory compliance = (VI / Approach Percentage)^2. Pennsylvania regulations cap maximum volatility at 10,000,000 plays. The VI concept applies primarily to slot machine design and regulatory approval.

One entry from the Casino Industry Glossary — 1,157 terms written for surveillance, compliance and operations professionals rather than for players. Definitions describe industry usage; where a term carries a regulatory meaning, verify against the instrument that governs your jurisdiction.