{"entity":{"id":"prespecified-vs-post-hoc","kind":"term","name":"Pre-specified vs post-hoc analysis","aka":["pre-specified","prespecified","pre-planned","prespecified analysis","pre-specified analysis","post-hoc","post hoc","post-hoc analysis","post-hoc subgroup","retrospective analysis","unplanned analysis","exploratory","exploratory analysis","hypothesis-generating","hypothesis generating","nominal","nominal P value","nominally significant","data dredging","p-hacking","statistical analysis plan","protocol-specified","pre-registered","pre-registration","preregistered","registered report","registered reports","statistical analysis plans"],"tldr":"Whether an analysis was planned and written down before the data were seen (pre-specified) or invented afterwards (post-hoc). Post-hoc findings, especially in subgroups, are prone to be chance and count as hypotheses for a new trial, not as evidence.","summary":"Trial protocols and statistical analysis plans, registered in advance (ClinicalTrials.gov, EU CTR), list the endpoints, populations and tests that will count; regulators approve on pre-specified analyses and treat post-hoc results as exploratory with 'nominal' P values. Post-hoc subgroup analyses have produced both misleading claims (retrospective PD-L1 cut-offs) and genuine discoveries later confirmed (KRAS wild-type for cetuximab). Pre-registration is standard in clinical trials and the site's ideas argue for extending it to animal studies and to 'silent trial' evaluations of AI, where the lack of pre-registration is a known source of false positives.","asOf":"2026-09-09","wikipedia":"https://en.wikipedia.org/wiki/Preregistration_(science)","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Preregistration_(science)"}],"tags":[],"related":["subgroup-analysis","statistical-significance","primary-endpoint","intention-to-treat","trial-registration","trial-protocol","trial-failure-modes","biomarker-stratified-design"],"cancers":[],"sections":["drug-discovery"],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":["magnitude","progesterone-preop-tmh","mindact"],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"Trials"},"route":"/terms/prespecified-vs-post-hoc/","neighbours":{"term":[{"id":"biomarker-stratified-design","kind":"term","name":"Enrichment and biomarker-stratified designs","route":"/terms/biomarker-stratified-design/"},{"id":"estimand","kind":"term","name":"Estimands and intercurrent events (ICH E9(R1))","route":"/terms/estimand/"},{"id":"intention-to-treat","kind":"term","name":"Intention-to-treat (ITT) and per-protocol analysis","route":"/terms/intention-to-treat/"},{"id":"p-value","kind":"term","name":"P-value","route":"/terms/p-value/"},{"id":"primary-endpoint","kind":"term","name":"Primary, secondary and co-primary endpoints","route":"/terms/primary-endpoint/"},{"id":"statistical-significance","kind":"term","name":"Statistical significance (P values, alpha, multiplicity)","route":"/terms/statistical-significance/"},{"id":"subgroup-analysis","kind":"term","name":"Subgroup analysis (forest plots)","route":"/terms/subgroup-analysis/"},{"id":"trial-protocol","kind":"term","name":"Trial protocol and statistical analysis plan","route":"/terms/trial-protocol/"},{"id":"trial-registration","kind":"term","name":"Trial registration and results reporting (ClinicalTrials.gov, EU CTR)","route":"/terms/trial-registration/"},{"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/"}],"trial":[{"id":"magnitude","kind":"trial","name":"MAGNITUDE","route":"/trials/magnitude/"},{"id":"mindact","kind":"trial","name":"MINDACT","route":"/trials/mindact/"},{"id":"progesterone-preop-tmh","kind":"trial","name":"Single-injection depot progesterone before breast surgery (Tata Memorial)","route":"/trials/progesterone-preop-tmh/"}]}}