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A curious likelihood identity for the multivariate t-distribution

 

作者: John T. Kent,   David E. Tyler,   Yahuda. Vard,  

 

期刊: Communications in Statistics - Simulation and Computation  (Taylor Available online 1994)
卷期: Volume 23, issue 2  

页码: 441-453

 

ISSN:0361-0918

 

年代: 1994

 

DOI:10.1080/03610919408813180

 

出版商: Marcel Dekker, Inc.

 

关键词: multivariate t-distribution;EM algorithm;robustness;uniqueness of maximum likelihood estimates

 

数据来源: Taylor

 

摘要:

It is shown that maximum likelihood estimates of the location vector and scatter matrix for a multivariate t-distribution in p dimensions with v≥1 degrees of freedom. can be identified with the maximum likelihood estimates for a scatter-only estimation problem from a (p+1)-dimensional multivariate the t-distribution with v−1>0 degrees of freedom. The t-distribution is only distribution for which this dual formulation is possible. Since the existence and uniqueness properties of maximum likelihood estimates are straightforward to prove for general scatter-only problems. we are able to immediately deduce existence and uniqueness results for the trickier location-scatter problem in the special case of the t-distribution. Each of these two formulations gives rise to an EM algorithm to maximize the likelihood. though the two algorithms are slightly different. The limiting Cauchy case v=1 requires some special treatment.

 

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