Abstract
We consider a linear mixed-effects model with a clustered structure, where the parameters are estimated using maximum likelihood (ML) based on possibly unbalanced data. Inference with this model is typically done based on asymptotic theory, assuming that the number of clusters tends to infinity with the sample size. However, when the number of clusters is fixed, classical asymptotic theory developed under a divergent number of clusters is no longer valid and can lead to erroneous conclusions. In this paper, we establish the asymptotic properties of the ML estimators of random-effects parameters under a general setting, which can be applied to conduct valid statistical inference with fixed numbers of clusters. Our asymptotic theorems allow both fixed effects and random effects to be misspecified, and the dimensions of both effects to go to infinity with the sample size.
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Acknowledgements
The research of Chih-Hao Chang is supported by ROC Ministry of Science and Technology grant MOST 107-2118-M-390-001. The research of Hsin-Cheng Huang is supported by ROC Ministry of Science and Technology grant MOST 106-2118-M-001-002-MY3. The research of Ching-Kang Ing is supported by the Science Vanguard Research Program under the Ministry of Science and Technology, Taiwan, ROC.
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Chang, CH., Huang, HC. & Ing, CK. Inference of random effects for linear mixed-effects models with a fixed number of clusters. Ann Inst Stat Math 74, 1143–1161 (2022). https://doi.org/10.1007/s10463-022-00825-7
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DOI: https://doi.org/10.1007/s10463-022-00825-7