ArticleStatistics in medicine2011
Avoiding bias in mixed model inference for fixed effects.
Article in Statistics in medicine, 2011. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 37 papers.
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Who cites it
37 citing papers in PubMed.
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- Risperidone added to parent training and stimulant medication: effects on attention-deficit/hyperactivity disorder, oppositional defiant disorder, conduct disorder, and peer aggression.Journal of the American Academy of Child and Adolescent Psychiatry · 2014Trial
- What does risperidone add to parent training and stimulant for severe aggression in child attention-deficit/hyperactivity disorder?Journal of the American Academy of Child and Adolescent Psychiatry · 2014Trial
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- The Relationship Between a Hospital's Magnet Status and LGBTQ+ Inclusivity in Policies and Practices in US Hospitals.Research in nursing & health · 2025Article
- Daytime physical activity and nighttime glucose levels in individuals with pregnancy hyperglycemia: linking wearable activity trackers to continuous glucose monitoring.Frontiers in endocrinology · 2025Article
- Power and sample size for reversible linear mixed models with clustering and longitudinality: GLIMMPSE Version 3.PloS one · 2025Article
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- Efficient computation of high-dimensional penalized generalized linear mixed models by latent factor modeling of the random effects.Biometrics · 2024Article
- glmmPen: High Dimensional Penalized Generalized Linear Mixed Models.The R journal · 2023Article
- Power and sample size analysis for longitudinal mixed models of health in populations exposed to environmental contaminants: a tutorial.BMC medical research methodology · 2023Review
- Analysis of multiple-period group randomized trials: random coefficients model or repeated measures ANOVA?Trials · 2022Article
- Psychological and behavioral responses during the COVID-19 pandemic among individuals with mobility and/or self-care disabilities.Disability and health journal · 2022Article
- Power and Sample Size for Fixed-Effects Inference in Reversible Linear Mixed Models.The American statistician · 2019Article
- On the Distribution of Summary Statistics for Missing Data.Communications in statistics: theory and methods · 2019Article
- Predictors of first ischemic lower limb ulcer in dialysis patients: an observational cohort study.Journal of nephrology · 2018Observational
- Internal pilot design for balanced repeated measures.Statistics in medicine · 2018Article
Corrections and comments
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Authors and funding
3 authors.
Funding
Abstract
Analysis of a large longitudinal study of children motivated our work. The results illustrate how accurate inference for fixed effects in a general linear mixed model depends on the covariance model selected for the data. Simulation studies have revealed biased inference for the fixed effects with an underspecified covariance structure, at least in small samples. One underspecification common for longitudinal data assumes a simple random intercept and conditional independence of the within-subject errors (i.e., compound symmetry). We prove that the underspecification creates bias in both small and large samples, indicating that recruiting more participants will not alleviate inflation of the Type I error rate associated with fixed effect inference. Enumerations and simulations help quantify the bias and evaluate strategies for avoiding it. When practical, backwards selection of the covariance model, starting with an unstructured pattern, provides the best protection. Tutorial papers can guide the reader in minimizing the chances of falling into the often spurious software trap of nonconvergence. In some cases, the logic of the study design and the scientific context may support a structured pattern, such as an autoregressive structure. The sandwich estimator provides a valid alternative in sufficiently large samples. Authors reporting mixed-model analyses should note possible biases in fixed effects inference because of the following: (i) the covariance model selection process; (ii) the specific covariance model chosen; or (iii) the test approximation.
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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.