Factorial sample size and multiplicity
Plan effect precision and testing
Plan power or precision for priority factor and interaction claims, including multiplicity. A design adequate for a marginal effect may be inadequate for an interaction.
Flow diagram
Steps
Prioritize confirmatory questions
Identify which main effects and interactions support claims.
Specify effect and variation scenarios
Use evidence for main and interaction contrasts separately.
Specify multiplicity strategy
Link error control to the planned family of claims.
Plan power for design and analysis
Account for combinations, imbalance, attrition and interaction assumptions.
Document limits of interaction inference
State when the design is not powered to detect important interaction.
Factorial sample size and multiplicity
End flow
Tables and supporting information
Factorial power scenarios
Main-effect power does not establish interaction power.
Assumptions and rationale
Absence of significant interaction does not prove absence of interaction; prespecify how uncertainty will be interpreted.
Method and protocol evidence
Attach the protocol, methodological sources and versioned software specification supporting these decisions. Record citations and provenance; do not enter participant identifiers.