Pitman–Koopman–Darmois, informal form

Theorem taught in Exponential families and conjugacy, part of Bayesian statistics

Pitman–Koopman–Darmois, informal form

Type Theorem
Taught in Exponential families and conjugacy
Part Bayesian statistics

For regular iid models with parameter-independent support, the theorem says, roughly, that the existence for every n of a sufficient statistic whose dimension stays fixed essentially characterises exponential families. The support condition matters: models such as \operatorname{Uniform}(0,\theta) can have a fixed-dimensional sufficient statistic without having the regular form Equation (3) in Exponential families and conjugacy.

Used in

See also

Sufficient statistic · Exponential family · Statistic and estimator · Fisher–Neyman factorisation · Minimal sufficiency · Complete statistic · Ancillary statistic · Basu’s theorem

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