Chapter 2
Principles of Decision Theory
2.1. Generalities
The examples given in Chapter 1 show that a statistical problem may be characterized by the following elements:
– a probability distribution that is not entirely known;
– observations;
– a decision to be made.
Formalization: Wald’s decision theory provided a common framework for statistics problems. We take:
1) A triplet
where P is a family of probabilities on the measurable space
is called a statistical model. We often set P = {Pθ, θ ∈ Θ} where we suppose that
is injective, and Θ is called the parameter space.
2) A measurable space
is called a decision (or action) space.
3) A set
of measurable mappings
is called a set of decision functions (d.f.) (or decision rules).
Description: From an observation that follows an unknown distribution P ∈ P, a statistician chooses an element a ∈ D using an element d from .
Preference relation ...
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