Multivariate mixed models with model-free random effects
Abstract
Linear mixed models are widely used to analyze non-independent data, but inference for fixed effects can be unreliable under misspecification of the random-effects distribution, inaccurate Fisher information estimation, or convergence failures, leading to a lack of control over false positives. These difficulties are amplified in multivariate settings, where within-cluster and between-response dependence must be modeled jointly. We propose a testing procedure for fixed effects in multivariate linear mixed models that avoids Fisher information estimation and does not require correct specification of the random-effects distribution by combining score statistics with clusterwise sign-flipping transformations. Our method accommodates both forms of dependence and yields asymptotically valid inference under weak distributional assumptions on the data-generating process.
Cite
@article{arxiv.2604.27907,
title = {Multivariate mixed models with model-free random effects},
author = {Angela Andreella and Livio Finos},
journal= {arXiv preprint arXiv:2604.27907},
year = {2026}
}