Provides nonparametric permutation tests for testing all or
any subset of random effects in linear and nonlinear mixed-effects
models, without requiring normality or other distributional
assumptions on random effects or errors. Three distribution-free
variance-component estimators are implemented: Variance Least
Squares ('VLS'), Method of Moments ('MM'), and Method of Moments
with First-Order Approximation ('MMF'). A permutation procedure is
used to obtain finite-sample p-values. Plotting functions support
data exploration, model evaluation, and communication of results.
Methods are described in Uwimpuhwe, Drikvandi, and Blozis (2026)