{"entity":{"id":"idea-tr2-animal-power-mandate","kind":"idea","name":"Pre-specified sample sizes for animal studies; no more 'representative' experiments","aka":[],"tldr":"Underpowered mouse experiments give exaggerated positive results and uninformative negatives, and papers often show one 'representative' result out of several attempts. Funders and journals should require a pre-specified power calculation, the number of independent repeats performed, and reporting of every repeat rather than the best one.","summary":"Underpowered animal studies produce exaggerated effects when positive and are uninformative when negative. Sample-size justification is required by ARRIVE and by ethics committees in principle but is rarely checked. Funders and journals could require a pre-specified power calculation, the number of independent repeats performed, and reporting of all repeats rather than a representative one.","asOf":"2026-09-08","links":[{"label":"ARRIVE guidelines","url":"https://arriveguidelines.org/"}],"tags":[],"related":["idea-tr2-arrive-audit"],"cancers":[],"sections":[],"technologies":["pdx-models"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":["b-reproducibility","b-preclinical-models"],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"hypothesis":"Enforcement increases the median group size in published in vivo efficacy studies and reduces reported effect sizes towards those seen in adequately powered replications.","rationale":"Effect-size inflation from small samples is a mathematical certainty under publication bias; the fix is procedural and cheap.","test":"Adopt at two funders; audit group sizes, repeat reporting and effect sizes in funded publications before and after.","maturity":"early-clinical","actor":"policy","cost":"small","horizonYears":1},"route":"/ideas/idea-tr2-animal-power-mandate/","neighbours":{"idea":[{"id":"idea-tr2-arrive-audit","kind":"idea","name":"Audit animal studies for randomisation and blinding, published by institution","route":"/ideas/idea-tr2-arrive-audit/"}],"technology":[{"id":"pdx-models","kind":"technology","name":"Patient-derived xenografts","route":"/technologies/pdx-models/"}],"bottleneck":[{"id":"b-preclinical-models","kind":"bottleneck","name":"Lab models that fail to predict what happens in patients","route":"/bottlenecks/b-preclinical-models/"},{"id":"b-reproducibility","kind":"bottleneck","name":"Preclinical results do not reproduce","route":"/bottlenecks/b-reproducibility/"}]}}