Fairness-enhancing mixed effects deep learning improves fairness on in-
  and out-of-distribution clustered (non-iid) data
Adam Wang Son Nguyen Albert Montillo
Traditional deep learning (DL) suffers from two core problems. Firstly, it
assumes training samples are independent and identically distributed. However,
numerous real-world datasets group samples by shared measurements (e.g., study
participants or cells), violating this assumption. In these scenarios, DL can
show compromised performance, limited generalization, and interpretability
issues, coupled with cluster confounding causing Type 1 and 2 errors. Secondly,
models are typically trained for overall accuracy, often neglecting
underrepresented groups and introducing biases in crucial areas like loan
approvals or determining health insurance rates, such biases can significantly
impact one's quality of life. To address both of these challenges
simultaneously, we present a mixed effects deep learning (MEDL) framework. MEDL
separately quantifies cluster-invariant fixed effects (FE) and cluster-specific
random effects (RE) through the introduction of: 1) a cluster adversary which
encourages the learning of cluster-invariant FE, 2) a Bayesian neural network
which quantifies the RE, and a mixing function combining the FE an RE into a
mixed-effect prediction. We marry this MEDL with adversarial debiasing, which
promotes equality-of-odds fairness across FE, RE, and ME predictions for
fairness-sensitive variables. We evaluated our approach using three datasets:
two from census/finance focusing on income classification and one from
healthcare predicting hospitalization duration, a regression task. Our
framework notably enhances fairness across all sensitive variables-increasing
fairness up to 82% for age, 43% for race, 86% for sex, and 27% for
marital-status. Besides promoting fairness, our method maintains the robust
performance and clarity of MEDL. It's versatile, suitable for various dataset
types and tasks, making it broadly applicable. Our GitHub repository houses the
implementation.