Decile
Also known as: Deciles · Decile band · Quantile · Percentile
Each of the ten 10% slices you get by ordering a base and cutting it into equal parts. In risk, the worst decile is the group of 10% with the worst scores.
Legal basis
Wikipedia — Decile
A decile is a special case of a quantile: order the cases by a measure — here, the score — and split them into ten equally sized groups. The first decile holds the 10% at one end; the tenth, the 10% at the other. It is the cut that gives enough resolution to see the tail without shattering the base into groups too small to measure.
In risk, almost every reading of a score runs through deciles: lift is computed by decile, the capture curve accumulates decile by decile, and the operational decision — decline, reprice, review acceptance — usually aims at the worst decile, where the event concentrates.
Frequently asked questions
What is the worst decile of a score?
It is the group made up of the 10% of cases with the worst scores, after ordering the whole base. It is where the event rate tends to be highest and where risk decisions have the most effect.