Factorial trial overview — Factorial randomized trial

Question

Define the intervention questions suitable for a joint factorial design.

Specify factors and interactions

Specify factor levels, combinations and marginal, simple or interaction contrasts on a named scale.

Protocol and registration

Prespecify estimands, multiplicity, safety and analysis; obtain approvals and register before enrollment.

Recruit

Apply eligibility for the relevant factor combinations and record consent.

Randomize combinations

Randomize eligible participants to combinations with concealed allocation and documented restrictions.

Follow

Track adherence and outcomes for each factor, including intercurrent events and harms.

Estimate planned effects

Estimate the prespecified factor and interaction contrasts with compatible intervals and multiplicity control.

Report

Report combinations, factor-specific receipt and the estimands analyzed using factorial reporting guidance.

Factorial trial overview

End flow

Protocol and decision register

Record the protocol, approvals and registration where applicable. Preserve planned decisions and amendments separately from results.

Protocol and rationale evidence

Attach the dated protocol, approvals and amendments. A clinical trial registry publicly records the trial plan, such as ClinicalTrials.gov or an eligible WHO primary registry such as ISRCTN. Record the registry name, identifier and registration date before first enrollment. WHO ICTRP is a search platform, not itself a registry. Registration does not imply randomization.