Glossary

Terms that recur across the entries, defined once here so the dated posts can stay short. Each definition is the plain sense used on this weblog rather than an attempt at a formal treatment.

Expected value

The average result per decision, obtained by weighting every possible outcome by its probability. A property of the process, not a prediction about any single instance of it.

House edge

The expected loss on a decision expressed as a percentage of the amount staked. Derived from the rules and the payout schedule, so it moves when either of those moves.

Return to player

The same quantity as house edge stated from the other side: the share of stakes returned rather than the share retained. The two always sum to the whole.

Hold

A measured figure comparing what a table or machine retained against what was brought to it over some period. Usually larger than the house edge, because money staked repeatedly meets the edge more than once.

Independent trial

An event whose probability is unaffected by the outcomes of earlier events. Wheels and coins qualify; a shoe dealt without reshuffling does not.

True odds

The ratio of ways an outcome can fail to ways it can occur. A wager paid at true odds has a neutral expected result on that portion of the stake.

Variance

A measure of how widely results spread around their average. Two games with the same edge can have very different variance and so feel very different over a short session.

Unit

A fixed fraction of an amount set aside in advance, used so that stake sizes can be compared across games and days. A bookkeeping device with no effect on any game's pricing.