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MSTest (version 0.1.9)

thetaSE_louis: Louis (1982) standard errors for Markov-switching models

Description

Computes standard errors using the expected complete-data information matrix B from Louis (1982). B = -Hessian(Q), where Q(theta) is the expected complete-data log-likelihood (the EM Q-function), evaluated at the converged parameter values with smoothed state probabilities held fixed.

The complete-data information B is typically better conditioned than the observed-data Hessian. Since I_obs = B - M where M >= 0 is the missing information, B >= I_obs (PSD), so B^{-1} slightly underestimates the true variance. The SEs are therefore slightly optimistic but numerically more stable, especially for weakly identified models.

Usage

thetaSE_louis(mdl)

Value

List provided as input with additional attributes theta_se, info_mat, and louis_used = TRUE.

Arguments

mdl

List with model properties (output from an MS model constructor). Must contain theta, St (smoothed probabilities), and model-specific fields.

References

Louis, T. A. (1982). "Finding the Observed Information Matrix When Using the EM Algorithm." Journal of the Royal Statistical Society, Series B, 44(2), 226-233.