Linked Questions

1 vote
0 answers
17 views

Interpreting rePCA [duplicate]

I have trainied a mixed model that is overfitting. We used lme4 and got this warning boundary (singular) fit: see ?isSingular and sure enough running isSingular as ...
Angus Campbell's user avatar
9 votes
1 answer
724 views

Parsimonious Mixed Models

I recently read a paper on the trimming of random effect structure by Bates, Kliegle, Vasishth and Baayen (2015). My understanding is that the Parsimonious Mixed Model they proposed mainly follows the ...
Chloe's user avatar
  • 363
5 votes
1 answer
2k views

Model not singular but doesn't converge what could be the reason (lme4 in R)

I'm following up on this great answer regarding running Principal Component Analysis (PCA) to uncover the reason behind lack of convergence and/or singularity for Mixed-Effects models. My model below ...
rnorouzian's user avatar
  • 4,016
5 votes
1 answer
621 views

Should I remove random intercepts from my model?

I have collected some data on response times (Y) under two varying conditions (X1 and X2). The conditions are continuous variables, although I set them to fixed values of 1,2,3,4 and 5. I have 10 ...
camhsdoc's user avatar
  • 369
6 votes
1 answer
949 views

When can we exclude random effects?

Random effects are useful for accounting for variance between groups (e.g., students within schools; patients within hospitals) or avoiding cases of pseudorelication with repeated measures data. But, ...
aquameer's user avatar
  • 111
1 vote
1 answer
2k views

Mixed model fails to converge - do I delete the random intercept or the random slope, and what does the variance of the random effects say?

I'm in the process of building my mixed models, and unfortunately I encountered a problem when creating the random effects structure. I have two random effects: ResponseId (i.e., participant number) ...
Ola_88's user avatar
  • 93
4 votes
1 answer
1k views

singular covariance matrices = estimates of zero random-effects variance in a model with random-intercepts

I was wondering why for mixed-effects models that have degenerate or singular covariance matrices (some linear combinations of the random effects are estimated to having no variability) are said to ...
rnorouzian's user avatar
  • 4,016
6 votes
1 answer
372 views

Is a singular fit with no correlations near +/- 1 or variances of zero, a false positive in lme4

Using lmer and glmer from lme4 sometimes get a "singular fit" warning when fitting mixed models, yet when I inspect the variance-covariance matrix of random effects, there are no ...
LeelaSella's user avatar
  • 2,040
4 votes
1 answer
389 views

R lmer model: add factors or reduce factors

In mixed effect models, do you add factors one by one? Or do you reduce the factors one by one? What I am doing is as follows. Are there any problems with the steps? Build a full model: ...
SuperDuperMario's user avatar
3 votes
1 answer
220 views

Corr of random-effects when a cross-level interaction in lme4

I had a quick question. I have a cross-level interaction in my model below (ses*sector). My cluster-level predictor ...
rnorouzian's user avatar
  • 4,016
3 votes
1 answer
84 views

Feasibility of Linear Mixed Effects Models (aka. MLM) after Unflattering Visual Inspection

Is it still of utility to run a full-blown LME modelling procedure when the visual inspections between the predictors and outcome variable are characterless? I have been arguing that it makes little ...
Rafs's user avatar
  • 441
4 votes
1 answer
44 views

Mixed model for trial-based analysis

I conducted an experiment that investigated preferences for two-digit numbers. Each digit was randomly drawn from a list of digits between 1 and 9, with one digit presented at a leftish position and ...
Lafayote's user avatar
  • 129
1 vote
1 answer
49 views

Parsimonious model - non convergent model decreases fit when removing random slope with near zero variance

I am trying to use Bates et al (2015) recommendation on reducing a maximal model based on variance explained by the random terms. Importantly, all examples in Bates are models with exclusively ...
Luminosa's user avatar
  • 111