Universal Domination and Stochastic Domination: U-Admissibility and U-Inadmissibility of the Least Squares Estimator

Loading...
Thumbnail Image
Penn collection
Statistics Papers
Degree type
Discipline
Subject
decision theory under a broad class of loss functions
James-Stein positive part estimator
admissibility
Statistics and Probability
Funder
Grant number
License
Copyright date
Distributor
Related resources
Author
Brown, Lawrence D
Hwang, Jiunn T
Contributor
Abstract

Assume the standard linear model Xn×1 = An×p θp×1 + εn×1, where ε has an n-variate normal distribution with zero mean vector and identity covariance matrix. The least squares estimator for the coefficient θ is θ^ ≡ (A′A)−1A′X. It is well known that θ^ is dominated by James-Stein type estimators under the sum of squared error loss |θ−θ^|2 when p ≥ 3. In this article we discuss the possibility of improving upon θ^, simultaneously under the "universal" class of losses: {L(|θ - θ^|) : L (.) any nondecreasing function} An estimator that can be so improved is called universally inadmissible (U-inadmissible). Otherwise it is called U-admissible. We prove that θ^ is U-admissible for any p when A′A = I. Furthermore, if A′A ≠ I, then θ^ is U-inadmissible if p is "large enough." In a special case, p ≥ 4 is large enough. The results are surprising. Implications are discussed.

Advisor
Date Range for Data Collection (Start Date)
Date Range for Data Collection (End Date)
Digital Object Identifier
Series name and number
Publication date
1989
Journal title
The Annals of Statistics
Volume number
Issue number
Publisher
Publisher DOI
Journal Issue
Comments
Recommended citation
Collection