Cited by 7,720Meta-analysis and systematic reviewsPsychology Research and BibliometricsStatistical Methods in Epidemiology

The DOI matches its Crossref record; 110 of the 110 references it cites were found in a registry or an index; 11 of the 39 sources its claims cite were checked for support.

Power failure: why small sample size undermines the reliability of neuroscience

Open access
Button, Katherine S., Ioannidis, John P. A., Mokrysz, Claire, Nosek, Brian A., Flint, Jonathan, Robinson, Emma S. J., Munafò, Marcus R.·2013·Nature Reviews Neuroscience

Abstract

A study with low statistical power has a reduced chance of detecting a true effect, but it is less well appreciated that low power also reduces the likelihood that a statistically significant result reflects a true effect. Here, we show that the average statistical power of studies in the neurosciences is very low. The consequences of this include overestimates of effect size and low reproducibility of results. There are also ethical dimensions to this problem, as unreliable research is inefficient and wasteful. Improving reproducibility in neuroscience is a key priority and requires attention to well-established but often ignored methodological principles.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This review argues that low statistical power is widespread in neuroscience and that it makes published findings less likely to be true, more likely to overstate effects, and harder to replicate. Across meta-analyses from several subfields, median power was often below 31%, with some estimates as low as 8%.

Key findings

  • In a sample of 48 articles, 49 meta-analyses and 730 primary studies, the median statistical power in neuroscience was 21%; excluding seven unusually high-powered neurological meta-analyses, it fell to 18%.
  • The observed number of nominally significant studies was 349, compared with 254 expected under the meta-analytic summary effects, indicating excess significance (p < 0.0001).
  • For brain volume studies, median power was 8% across 461 individual studies from 41 meta-analyses in eight articles; for animal water-maze and radial-maze studies, median power was 18% and 31%, respectively, with average sample sizes of 22 and 24 animals.
  • With pre-study odds of 0.25 and α = 0.05, 20% power yielded a positive predictive value of 0.50, whereas 80% power yielded 0.80; simulations suggested initial effect estimates from studies powered between about 8% and 31% are inflated by 25% to 50%.

Methods

  • The authors searched Web of Science on 2 February 2012 for 2011 articles using the terms “neuroscience” and “meta-analysis,” screened records independently, and included 48 articles containing 49 meta-analyses and 730 primary studies.
  • They extracted summary effect sizes and study-level sample sizes or event counts, then calculated each primary study’s achieved power to detect its corresponding meta-analytic summary effect at α = 5% using G*Power, reporting mean and median power and testing for excess significance.
  • Because the main sample underrepresented neuroimaging and animal-model research, they added representative meta-analyses from those areas outside the 2011 sampling frame.

Limitations

  • The paper states that true effect sizes are unknown, so meta-analytic summary effects were used as proxies; because those summaries may themselves be inflated by publication and other biases, the power estimates are likely optimistic.
  • The authors note that the main analysis underrepresented neuroimaging and animal-model subfields, and that the animal-model findings rest on only two meta-analyses, so extrapolation should be cautious.
  • Evident from the text: the search was limited to 2011 Web of Science records and to meta-analyses with extractable data, and the excess-significance test depends on the assumption that the summary effects approximate the true effects.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/nrn3475

Cites

110 of 110 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

11 of 39 cited sources checked · 6 supported · 0 flagged · accuracy not yet measured

Show all 66 claims

  • It may state two separate claims as one. 21
  • Probably not a substantial claim. 19
34 of 34
  • The authors state this as an assumption.

    The summary effect size reported in each study is close to the true effect size.

    “Importantly, these calculations assume that the summary effect size reported in each study is close to the true effect size, but it is likely that they are inflated owing to publication and other biases described above.”
  • The authors state this as an assumption.

    The initially observed effect we are trying to replicate reflects the true effect.

    “Assuming, as one might in a power calculation, that the initially observed effect we are trying to replicate reflects the true effect, the potential distribution of these replication effect estimates would be similar to the distribution of the original study (dashed green curve).”
  • The paper relies on this without support.

    The 49 meta-analyses included are representative of neuroscience research.

    “Our results indicate that the median statistical power in neuroscience is 21%.”
  • The paper relies on this without support.

    Most structural and volumetric MRI studies are very small and have minimal power to detect differences between compared groups.

    “Most structural and volumetric MRI studies are very small and have minimal power to detect differences between compared groups (for example, healthy people versus those with mental health diseases).”
  • The paper relies on this without support.

    The effects now sought in neuroscience experiments are often smaller and more subtle than before.

    “A consequence of the remarkable growth in neuroscience over the past 50 years has been that the effects we now seek in our experiments are often smaller and more subtle than before as opposed to when mostly easily discernible 'low-hanging fruit' were targeted.”
  • The paper relies on this without support.

    Computational analysis of very large datasets is now relatively straightforward, so that an enormous number of tests can be run in a short time on the same dataset.

    “At the same time, computational analysis of very large datasets is now relatively straightforward, so that an enormous number of tests can be run in a short time on the same dataset.”
  • The paper relies on this without support.

    These dramatic advances in the flexibility of research design and analysis have occurred without accompanying changes to other aspects of research design, particularly power.

    “These dramatic advances in the flexibility of research design and analysis have occurred without accompanying changes to other aspects of research design, particularly power.”
  • The paper relies on this without support.

    Low power is a problem in practice because of the normative publishing standards for producing novel, significant, clean results and the ubiquity of null hypothesis significance testing as the means of evaluating the truth of research findings.

    “Low power is a problem in practice because of the normative publishing standards for producing novel, significant, clean results and the ubiquity of null hypothesis significance testing as the means of evaluating the truth of research findings.”
  • The authors state this as an assumption.

    The initially observed effect that a replication study attempts to replicate reflects the true effect.

    “Assuming, as one might in a power calculation, that the initially observed effect we are trying to replicate reflects the true effect”
  • The paper relies on this without support.

    In an exploratory research field such as much of neuroscience, the pre-study odds are often low.

    “Notably, in an exploratory research field such as much of neuroscience, the pre-study odds are often low.”
10 of 10

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Detectable effect sizes are reversed for the two animal-study sample sizes

    Minor

    The animal-model section assigns d = 1.20 to n = 22 and d = 1.26 to n = 24 at 80% power. The ethical-implications section assigns the same effect sizes to the opposite sample sizes, changing which effect each typical study could detect.

1 of 1

Cited works that were retracted

Works this paper cites that were later retracted, from the retraction notices publishers deposit. Major when the notice came out before this paper was published.

  • Cites a retracted work: 10.1128/iai.05661-11

    Info

    The cited work was retracted; the date of the notice is not on record.

    Cited work 10.1128/iai.05661-11 · retraction date not known · this paper published 2013-04-10

1 of 1

Citations

Cites

1 retracted

Flagged first, then by citations

Show all 106 references

Research works printed but not linked: 2

  1. David, S. P. et al. Potential reporting bias in small fMRI studies of the brain. PLoS Biol. (in the press).
  2. Ioannidis, J. P., Tarone, R. & McLaughlin, J. K. The false-positive to false-negative ratio in epidemiologic studies. Epidemiology 22, 450–456 (2011). · DOI · Paper page

Cited by

Sorted by citations

Items 6,301–6,400 of 7,720

Metadata

Authors
Button, K. S., Ioannidis, J. P. A., Mokrysz, C., Nosek, B. A., Flint, J., Robinson, E. S. J., & Munafò, M. R.
Affiliations
  • University of Bristol (GB)
  • Stanford Medicine (US)
  • University of Virginia (US)
Venue
Nature Reviews Neuroscience
Published
2013-04-10
Volume
14
Issue
5
Pages
365-376
ISSN
  • 1471-003X (ISSN-L)
  • 1471-0048
OpenAlex
W2105824687
Cited by
7,641
References
106
Citations by year
2026: 584 · 2025: 611 · 2024: 606 · 2023: 553 · 2022: 658 · 2021: 692 · 2020: 752 · 2019: 683 · 2018: 679 · 2017: 597 · 2016: 486 · 2015: 352 · 2014: 268 · 2013: 109
FWCI
82.23
Type
journal article
Language
en
Update notices
erratum (2013-04-15)
Open access
Locations
  • Nature reviews. Neuroscience (publishedVersion)
  • PubMed (publishedVersion)
  • Explore Bristol Research (submittedVersion)
  • UCL Discovery (University College London) (submittedVersion)
Funders
  • Wellcome Trust (090532)
  • United Kingdom Clinical Research Collaboration
  • Cancer Research UK
  • National Institute for Health and Care Research
  • British Heart Foundation
  • Medical Research Council
  • Economic and Social Research Council
Topics
  • Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
  • Social Sciences › Psychology › Experimental and Cognitive Psychology › Psychology Research and Bibliometrics
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
Keywords
statistical power, small sample size, effect size overestimation, reproducibility, research ethics, research waste, research practices, brain research
MeSH terms
Humans, Neurosciences, Probability, Reproducibility of Results, Sample Size

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

A language model drew the claims from the paper on 2026-10-11, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

A second model labelled each claim on 2026-10-11 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).

Cited sources are checked with a language model’s help (gpt-6-sol).

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review