© 1982 by Biometrika Trust
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Finding maximum likelihood estimates of patterned covariance matrices by the EM algorithm
Educational Testing Service, Princeton New Jersey, U.S.A.
Graduate School of Management, Rutgers University Newark, New Jersey, U.S.A
Some patterned covariance matrices used to model multivariate normal data that do not have explicit maximum likelihood estimates can be viewed as submatrices of larger patterned covariance matrices that do have explicit maximum likelihood estimates. In such cases, the smaller covariance matrix can be viewed as the covariance matrix for observed variables and the larger covariance matrix can be viewed as the covariance matrix for both observed and missing variables. The advantage of this perspective is that the em algorithm can be used to calculate the desired maximum likelihood estimates for the original problem. Two examples are presented.
Key Words: Circular symmetry EM algorithm Maximum likelihood Missing data Patterned covariance matrix Stationary covariance
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