varTestnlme: An R Package for Variance Components Testing in Linear and Nonlinear Mixed-Effects Models

varTestnlme: An R Package for Variance Components Testing in Linear and Nonlinear Mixed-Effects Models

generalized mixed-effects models, nonlinear mixed-effects models, variance components, likelihood ratio test, random effects, R.

The issue of variance components testing arises naturally when building mixed-effects
models, to decide which effects should be modeled as fixed or random or to build parsimonious models. While tests for fixed effects are available in R for models fitted with lme4,
tools are missing when it comes to random effects. The varTestnlme package for R aims
at filling this gap. It allows to test whether a subset of the variances and covariances corresponding to a subset of the random effects, are equal to zero using asymptotic property
of the likelihood ratio test statistic. It also offers the possibility to test simultaneously
for fixed effects and variance components. It can be used for linear, generalized linear
or nonlinear mixed-effects models fitted via lme4, nlme or saemix. Numerical methods
used to implement the test procedure are detailed and examples based on different real
datasets using different mixed models are provided. Theoretical properties of the used
likelihood ratio test are recalled.

Charlotte Baey

https://www.jstatsoft.org/article/view/v107i06

generalized mixed-effects models, nonlinear mixed-effects models, variance components, likelihood ratio test, random effects, R.

September 2023

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