{"entity":{"id":"statistical-significance","kind":"term","name":"Statistical significance (P values, alpha, multiplicity)","aka":["statistically significant","statistical significance","not statistically significant","did not reach statistical significance","P value","p-value","P<0.05","P = 0.05","one-sided","two-sided","alpha spending","alpha allocation","type I error","multiplicity","multiple comparisons","hierarchical testing","gatekeeping","Bonferroni","powered","underpowered","sample size","statistical power","80% power","90% power","numerically","numerical improvement","trend toward","trend towards","clinically meaningful","clinical significance","sample sizes"],"tldr":"A result is 'statistically significant' when it would be unlikely (usually under 5%) to arise by chance if the treatment did nothing. It is a threshold, not a measure of benefit size: a tiny gain can pass it in a huge trial and a large one can miss it in a small trial, so ESMO and ASCO grade benefit separately.","summary":"Trials are sized ('powered') to detect a pre-specified effect with 80-90% probability at a 5% two-sided alpha; testing several endpoints or several interim looks would inflate false positives unless alpha is split (allocated) or spent sequentially, so hierarchical testing means a secondary endpoint cannot be claimed if a higher one failed. 'Numerically better', 'trend' and 'nominal P' are phrases for results that did not meet the pre-set bar. Clinical meaningfulness is separate: ASCO and ESMO scales (ESMO-MCBS) grade the size of benefit, and a significant 6-week PFS gain may not matter to patients. Confidence intervals convey both size and uncertainty and are preferred to bare P values.","asOf":"2026-09-09","wikipedia":"https://en.wikipedia.org/wiki/Statistical_significance","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Statistical_significance"}],"tags":[],"related":["primary-endpoint","prespecified-vs-post-hoc","subgroup-analysis","non-inferiority","hazard-ratio","group-sequential-design","sample-size-re-estimation","bayesian-trial-design","trial-failure-modes","p-value","confidence-interval"],"cancers":[],"sections":["drug-discovery"],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"Trials"},"route":"/terms/statistical-significance/","neighbours":{"term":[{"id":"bayesian-trial-design","kind":"term","name":"Bayesian trial design","route":"/terms/bayesian-trial-design/"},{"id":"confidence-interval","kind":"term","name":"Confidence interval","route":"/terms/confidence-interval/"},{"id":"futility","kind":"term","name":"Futility analysis (stopped for futility)","route":"/terms/futility/"},{"id":"group-sequential-design","kind":"term","name":"Group sequential design, stopping rules and alpha spending","route":"/terms/group-sequential-design/"},{"id":"hazard-ratio","kind":"term","name":"Hazard ratio (HR)","route":"/terms/hazard-ratio/"},{"id":"interim-analysis","kind":"term","name":"Interim analysis, readout and data cut-off","route":"/terms/interim-analysis/"},{"id":"non-inferiority","kind":"term","name":"Non-inferiority trial","route":"/terms/non-inferiority/"},{"id":"p-value","kind":"term","name":"P-value","route":"/terms/p-value/"},{"id":"prespecified-vs-post-hoc","kind":"term","name":"Pre-specified vs post-hoc analysis","route":"/terms/prespecified-vs-post-hoc/"},{"id":"primary-endpoint","kind":"term","name":"Primary, secondary and co-primary endpoints","route":"/terms/primary-endpoint/"},{"id":"sample-size-re-estimation","kind":"term","name":"Statistical power, sample size and re-estimation","route":"/terms/sample-size-re-estimation/"},{"id":"subgroup-analysis","kind":"term","name":"Subgroup analysis (forest plots)","route":"/terms/subgroup-analysis/"},{"id":"trial-failure-modes","kind":"term","name":"Why trials fail: underpowered, wrong endpoint, control arm drift, subgroup fishing, crossover","route":"/terms/trial-failure-modes/"}],"section":[{"id":"drug-discovery","kind":"section","name":"Drug Discovery Platforms","route":"/fronts/drug-discovery/"}]}}