## How do you read mixed effect model results?

Interpret the key results for Fit Mixed Effects Model

- Step 1: Determine whether the random terms significantly affect the response.
- Step 2: Determine whether the fixed effect terms significantly affect the response.
- Step 3: Determine how well the model fits your data.

**What does LMER mean in R?**

linear mixed-effects models

Abstract. Maximum likelihood or restricted maximum likelihood (REML) estimates of the pa- rameters in linear mixed-effects models can be determined using the lmer function in the lme4 package for R.

### How do you know if a random effect is significant?

To do this, you compare the log-likelihoods of models with and without the appropriate random effect – if removing the random effect causes a large enough drop in log-likelihood then one can say the effect is statistically significant.

**What is the difference between LMER and Glmer?**

The lmer() function is for linear mixed models and the glmer() function is for generalized mixed models.

#### What does linear mixed model tell you?

Linear mixed models are an extension of simple linear models to allow both fixed and random effects, and are particularly used when there is non independence in the data, such as arises from a hierarchical structure. For example, students could be sampled from within classrooms, or patients from within doctors.

**What package is LMER in?**

Eigen package

lme4 uses modern, efficient linear algebra methods as implemented in the Eigen package, and uses reference classes to avoid undue copying of large objects; it is therefore likely to be faster and more memory-efficient than nlme.

## What is Theta LMER?

In the parameterization that lme4 uses, the θ vector represents the (columnwise unpacking of) the lower triangle of the Cholesky factor of the variance-covariance matrix Σ: for example, in the 2 × 2 random-slopes case we have Σ=(θ10θ2θ3)(θ1θ20θ3)=(θ21θ1θ2θ1θ2θ22+θ23)=(σ21σ12σ12σ22)

**How many levels should a random effect have?**

This guideline that random effects terms should have at least five levels (i.e. groups) is backed by only limited empirical evidence (Harrison, 2015), but it is intuitive that too few draws from distribution will hinder one’s ability to estimate the variance of that distribution.

### Does Glmer use REML?

Glmer() always uses Maximum Likelihood (ML) rather than REstricted Maximum Likelihood (REML) (http://glmm.wikidot.com/faq#reml-glmm).