Odds
Odds express probability as a ratio p divided by (1 minus p).
Definition
Odds express probability as a ratio: odds equal p divided by (1 minus p), for probabilities strictly between 0 and 1. Odds are useful in Bayes updates and in model outputs.
Why it matters
Odds make some calculations simpler. For example, Bayes updates multiply odds by a likelihood ratio to produce posterior odds.
Common pitfalls
Using odds at 0 or 1: Odds are undefined at exactly 0 percent or 100 percent.
Mixing odds and probability: Always label which representation you use.