ArticlePLoS biology2018
What exactly is 'N' in cell culture and animal experiments?
Article in PLoS biology, 2018. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 169 papers, 4 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
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.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
169 citing papers in PubMed, 4 syntheses or guidelines pooled it.
- Fecal microbiota transplantation from psychiatric patients to mice - systematic review of methodologies and a call for standardization.Translational psychiatry · 2026Pooled it
- A host of issues: pseudoreplication in host-microbiota studies.Applied and environmental microbiology · 2024Pooled it
- Initial recommendations for performing, benchmarking and reporting single-cell proteomics experiments.Nature methods · 2023Guideline
- Conventional laboratory housing increases morbidity and mortality in research rodents: results of a meta-analysis.BMC biology · 2022Pooled it
- Integrating Physiological Biomarkers into Precision Livestock Farming for Laying Hens: Methodological Challenges and Future Research Directions.Animals : an open access journal from MDPI · 2026Review
- Clarifying the Experimental Unit and the Evidence for Preserved Osseointegration in a Zirconia-Silver Coating Study.Annals of biomedical engineering · 2026Article
- Exploratory Comparison of Behavior and Welfare-Related Indicators in Captive Lions (Animals : an open access journal from MDPI · 2026Article
- Systemic AR-C155858 During Fixed Treadmill Exercise in MPTP Mice: An Exploratory Study.Neurochemical research · 2026Article
- Structural Analysis of an Inulin-Type Fructan fromMolecules (Basel, Switzerland) · 2026Article
- Irritable Bowel Disease: Think Malonic and Methylmalonic Aciduria (CMAMMA)!JIMD reports · 2026Article
- Zingerone attenuates aluminum chloride/D-galactose-induced hippocampal neurotoxicity in mice: Modulation of oxidative stress, astrogliosis, cholinergic function, ATP hydrolysis, and neurotrophic signaling.Naunyn-Schmiedeberg's archives of pharmacology · 2026Article
- Time-Dependent Multimechanistic Antitumor Effects of Olive Oil Phenolics in a Triple-Negative Breast Cancer Mouse Model.Nutrients · 2026Article
- Increasing usable reads in RNA-seq protocols.iScience · 2026Article
- Black Cumin Seed Oil Disrupts Structural Biomass and Attenuates Porphyrin-Associated Maturation in Mature Oral Microcosm Biofilms: An In Vitro Study.Biomedicines · 2026Article
- Data Analysis Planning and Reporting for Confirmatory Multi-Lab Preclinical Trials: A Tutorial.Biometrical journal. Biometrische Zeitschrift · 2026Review
- grafify online: A web app for graphing and statistical analysis.PLoS biology · 2026Article
- Genes Associated With Fracture Risk in Thoroughbred Horses Have Novel Roles in Osteogenesis.Animal genetics · 2026Article
- A combination of artemisinin, moxidectin, and doxorubicin drugs can selectively and efficiently induce apoptosis in acute lymphoblastic and chronic myeloid leukemia cells in vitro and ex vivo.Medical oncology (Northwood, London, England) · 2026Article
- Neuroprotective Potential ofBiomolecules · 2026Article
- PCOS Serum Promotes Endometrial Cancer Cell Proliferation with Partial Involvement of IGF-Associated AKT/mTOR Signaling: A Pilot Translational Study with Exploratory Molecular Insights.International journal of molecular sciences · 2026Article
109 more citing papers are in PubMed but not listed here.
Corrections and comments
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Authors and funding
3 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Biologists determine experimental effects by perturbing biological entities or units. When done appropriately, independent replication of the entity-intervention pair contributes to the sample size (N) and forms the basis of statistical inference. If the wrong entity-intervention pair is chosen, an experiment cannot address the question of interest. We surveyed a random sample of published animal experiments from 2011 to 2016 where interventions were applied to parents and effects examined in the offspring, as regulatory authorities provide clear guidelines on replication with such designs. We found that only 22% of studies (95% CI = 17%-29%) replicated the correct entity-intervention pair and thus made valid statistical inferences. Nearly half of the studies (46%, 95% CI = 38%-53%) had pseudoreplication while 32% (95% CI = 26%-39%) provided insufficient information to make a judgement. Pseudoreplication artificially inflates the sample size, and thus the evidence for a scientific claim, resulting in false positives. We argue that distinguishing between biological units, experimental units, and observational units clarifies where replication should occur, describe the criteria for genuine replication, and provide concrete examples of in vitro, ex vivo, and in vivo experimental designs.
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What OpenQuestion holds
Registered trials
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.