Cited by 114Statistical Methods and Bayesian InferenceStatistics Education and MethodologiesEducational Research and Methods

Students Are Rarely Independent: When, Why, and How to Use Random Effects in Discipline-Based Education Research

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Theobald, Elli·2018·CBE—Life Sciences Education

Abstract

Discipline-based education researchers have a natural laboratory—classrooms, programs, colleges, and universities. Studies that administer treatments to multiple sections, in multiple years, or at multiple institutions are particularly compelling for two reasons: first, the sample sizes increase, and second, the implementation of the treatments can be intentionally designed and carefully monitored, potentially negating the need for additional control variables. However, when studies are implemented in this way, the observations on students are not completely independent; rather, students are clustered in sections, terms, years, or other factors. Here, I demonstrate why this clustering can be problematic in regression analysis. Fortunately, nonindependence of sampling can often be accounted for with random effects in multilevel regression models. Using several examples, including an extended example with R code, this paper illustrates why and how to implement random effects in multilevel modeling. It also provides resources to promote implementation of analyses that control for the nonindependence inherent in many quasi-random sampling designs.

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  1. Rosenthal R. Rosnow R. (1975). The volunteer subject. Wiley: New York.

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Authors
Theobald, E.
Affiliations
University of Washington (US)
Corresponding author
Theobald, Elli
Venue
CBE—Life Sciences Education
Published
2018-09
Volume
17
Issue
3
Pages
rm2
ISSN
1931-7913 (ISSN-L)
OpenAlex
W2888039885
Cited by
114
References
25
Citations by year
2026: 11 · 2025: 13 · 2024: 15 · 2023: 17 · 2022: 16 · 2021: 23 · 2020: 9 · 2019: 9 · 2018: 1
FWCI
8.71
Type
journal article
Language
en
Open access
Licence
cc-by-nc-sa
Locations
  • CBE—Life Sciences Education (publishedVersion, cc-by-nc-sa)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by-nc-sa)
  • PubMed Central (publishedVersion, cc-by-nc-sa)
  • PubMed (publishedVersion)
Funders
University of Washington
Topics
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods and Bayesian Inference
  • Physical Sciences › Mathematics › Statistics and Probability › Statistics Education and Methodologies
  • Social Sciences › Education › Educational Research and Methods
Keywords
random effects, multilevel regression, student clustering, treatment implementation, discipline-based education research
MeSH terms
Humans, Random Allocation, Research Design, Science, Students, Cluster Analysis, Multilevel Analysis

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