Odds, Probability & Bankroll
Odds vs odds ratio
Odds are the ratio of the probability of an event to the probability of it not happening. An odds ratio (OR) compares two sets of odds across different groups.
Key points
- Odds describe a single group; odds ratio compares two groups by dividing one group's odds by the other's.1
- An odds ratio of 1 indicates no association; values above or below 1 show higher or lower odds in the exposed group.2
- Odds ratio is a measure of association, not a direct probability, and is commonly used in medical studies and logistic regression.3
Where this term is used
Related terms
Odds & probability
Odds
Explains odds as a single-group ratio of event to non-event.
Odds & probability
Betting odds
Covers how odds are used in gambling to represent payout and implied probability.
Odds & probability
Fractional odds to decimal
Shows how to convert between fractional and decimal betting odds formats.
Odds & probability
Odds vs probability
Distinguishes odds from probability, two related but different measures.
Odds & probability
American odds
Explains the American odds format used primarily in US sportsbooks.
Odds & probability
Fractional odds
Describes fractional odds, the traditional format in UK horse racing and football.
Sources
- Making sense of odds and odds ratios pubmed.ncbi.nlm.nih.gov Defines odds as probability of event divided by probability of non-event.
- Odds Ratio - StatPearls - NCBI Bookshelf ncbi.nlm.nih.gov Provides the odds ratio formula and explains that OR=1 means no difference.
- Explaining Odds Ratios - PMC - NIH pmc.ncbi.nlm.nih.gov States that odds ratio compares two sets of odds and is a measure of association.
Sources are drawn from regulators, universities and published research, and each one is labelled with what it actually is — a preprint is not called a paper. Bookmaker and affiliate pages are never cited here, because a page that sells betting is not a neutral authority on it.