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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.
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.
Shares P-value, Statistical significance (P values, alpha, multiplicity), Primary, secondary and co-primary endpoints, Trial protocol and statistical analysis plan.
Shares Statistical significance (P values, alpha, multiplicity), Primary, secondary and co-primary endpoints, MAGNITUDE, Why trials fail: underpowered, wrong endpoint, control arm drift, subgroup fishing, crossover.
Shares Intention-to-treat (ITT) and per-protocol analysis, Statistical significance (P values, alpha, multiplicity), Estimands and intercurrent events (ICH E9(R1)), Why trials fail: underpowered, wrong endpoint, control arm drift, subgroup fishing, crossover.
Shares Intention-to-treat (ITT) and per-protocol analysis, Estimands and intercurrent events (ICH E9(R1)), Why trials fail: underpowered, wrong endpoint, control arm drift, subgroup fishing, crossover.
Shares P-value, Intention-to-treat (ITT) and per-protocol analysis, Estimands and intercurrent events (ICH E9(R1)), Why trials fail: underpowered, wrong endpoint, control arm drift, subgroup fishing, crossover.
Shares P-value, Statistical significance (P values, alpha, multiplicity).
Shares P-value, Statistical significance (P values, alpha, multiplicity).
Shares Subgroup analysis (forest plots), Enrichment and biomarker-stratified designs.