ArticlePeerJ2022
Should I use fixed effects or random effects when I have fewer than five levels of a grouping factor in a mixed-effects model?
Article in PeerJ, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 44 papers, 1 of them a synthesis that pooled it.
What it found
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Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
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Who cites it
44 citing papers in PubMed, 1 synthesis or guideline pooled it.
- Systematic review and meta-analysis of Murray's law in the coronary arterial circulation.American journal of physiology. Heart and circulatory physiology · 2024Pooled it
- Patient adherence and response time in electronic patient-reported outcomes: insights from three longitudinal clinical trials.Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation · 2024Trial
- Development of a mixed-effects longitudinal spline regression method for growth data analysis.MethodsX · 2026Article
- Cue-Based Authenticity Appraisals in Limited-Verifiability Contexts: A Two-Study Test in Historic Automotive Events.Behavioral sciences (Basel, Switzerland) · 2026Article
- Unveiling the interactions between design optimization, modeling strategies, and spatial analysis in genomic selection.TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik · 2026Article
- Fixed or Random Effects: Analysis of Clustered Data.Statistics in medicine · 2026Article
- Determining the impact of cannabis use on tobacco cessation: Results from a prospective non-randomized tobacco treatment trial.Addiction (Abingdon, England) · 2026Article
- Core concepts in statistics and research methods. Part 7: regression.BJA education · 2026Review
- Invasive Fishes Interact With Temperature to Reshape Community Size Structure Across Climatic Zones.Global change biology · 2026Article
- Sustained Transcriptional Response to Lipopolysaccharide and Interleukin-4 in an Immortalized Mouse Microglial Cell Line.Molecular neurobiology · 2026Article
- A pan-cancer compendium of 1,294 plasma cell-free DNA methylomes and fragmentomes enabling multicancer detection.Nature cancer · 2026Article
- Multimodal Wearable Monitoring of Exercise in Isolated, Confined, and Extreme Environments: A Standardized Method.Methods and protocols · 2026Article
- Risk factors of decisional conflict among people living with chronic pain identified through a pan-Canadian survey.Scientific reports · 2025Article
- Exposure to Rivals Does Not Affect Male Mate Choice inEcology and evolution · 2025Article
- Invasive goldfish (Carassius auratus) maintain aerobic scope across acute warm water temperatures.Biology open · 2025Article
- When a mean can be meaningless: evaluating mosquito infections withParasitology · 2025Review
- Association between postpartum systemic inflammation and serum calcium in healthy multiparous dairy cows: An exploratory observational analysis.JDS communications · 2025Article
- Enhancing systemic lupus erythematosus treatment outcomes with an early initiation of belimumab: insights from a multicenter retrospective study within the first five years.Arthritis research & therapy · 2025Article
- Exploring health outcome disparities in African regional economics communities: a multilevel linear mixed-effect analysis.BMC public health · 2025Article
- Early life stage bottleneck determines rates of coral recovery following severe disturbance.Ecology · 2025Article
Corrections and comments
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Authors and funding
1 author.
Funding
No grant is acknowledged in the PubMed record.
Abstract
As linear mixed-effects models (LMMs) have become a widespread tool in ecology, the need to guide the use of such tools is increasingly important. One common guideline is that one needs at least five levels of the grouping variable associated with a random effect. Having so few levels makes the estimation of the variance of random effects terms (such as ecological sites, individuals, or populations) difficult, but it need not muddy one's ability to estimate fixed effects terms-which are often of primary interest in ecology. Here, I simulate datasets and fit simple models to show that having few random effects levels does not strongly influence the parameter estimates or uncertainty around those estimates for fixed effects terms-at least in the case presented here. Instead, the coverage probability of fixed effects estimates is sample size dependent. LMMs including low-level random effects terms may come at the expense of increased singular fits, but this did not appear to influence coverage probability or RMSE, except in low sample size (
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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.