decision theory Decision theory (or the theory of choice; not to be confused with choice theory) is a branch of applied probability theory concerned with the theory of making decisions based on assigning probabilities to various factors and assigning numerical ...

, a decision rule is said to dominate another if the performance of the former is sometimes better, and never worse, than that of the latter. Formally, let

\delta_1

and

\delta_2

be two decision rules, and let

R(\theta, \delta)

be the

risk In simple terms, risk is the possibility of something bad happening. Risk involves uncertainty about the effects/implications of an activity with respect to something that humans value (such as health, well-being, wealth, property or the environme ...

of rule

\delta

for parameter

\theta

. The decision rule

\delta_1

is said to dominate the rule

\delta_2

R(\theta,\delta_1)\le R(\theta,\delta_2)

for all

\theta

, and the inequality is strict for some

\theta

.. This defines a

partial order In mathematics, especially order theory, a partially ordered set (also poset) formalizes and generalizes the intuitive concept of an ordering, sequencing, or arrangement of the elements of a set. A poset consists of a set together with a binary ...

on decision rules; the

maximal element In mathematics, especially in order theory, a maximal element of a subset ''S'' of some preordered set is an element of ''S'' that is not smaller than any other element in ''S''. A minimal element of a subset ''S'' of some preordered set is def ...

s with respect to this order are called ''

admissible decision rule In statistical decision theory, an admissible decision rule is a rule for making a decision such that there is no other rule that is always "better" than it (or at least sometimes better and never worse), in the precise sense of "better" define ...

s.''

References

{{statistics-stub Decision theory