# Decision rule

Talk0*34,139*pages on

this wiki

Assessment |
Biopsychology |
Comparative |
Cognitive |
Developmental |
Language |
Individual differences |
Personality |
Philosophy |
Social |

Methods |
Statistics |
Clinical |
Educational |
Industrial |
Professional items |
World psychology |

**Statistics:**
Scientific method ·
Research methods ·
Experimental design ·
Undergraduate statistics courses ·
Statistical tests ·
Game theory ·
Decision theory

In decision theory, a **decision rule** is a function which maps an observation to an appropriate action. Decision rules play an important role in the theory of statistics and economics, and are closely related to the concept of a strategy in game theory.

In order to evaluate the usefulness of a decision rule, it is necessary to have a loss function detailing the outcome of each action under different states.

## Formal definition Edit

Given an observable random variable *X* over the probability space , determined by a parameter *θ* ∈ *Θ*, and a set *A* of possible actions, a (deterministic) **decision rule** is a function *δ* : → *A*.

## Examples of decision rules Edit

- An estimator is a decision rule used for estimating a parameter. In this case the set of actions is the parameter space, and a loss function details the cost of the discrepancy between the true value of the parameter and the estimated value.
- Out of sample prediction in regression and classification models.

## See also Edit

This page uses Creative Commons Licensed content from Wikipedia (view authors). |