Resolution is the length of the shortest word in a design's defining relation. In a resolution III design, main effects are aliased with two-factor interactions; resolution IV keeps main effects clear of two-factor interactions but aliases those interactions with each other; resolution V keeps both main effects and two-factor interactions clear. Higher resolution costs more runs, so screening work often accepts III or IV and follows up later.
Res III is fine for screening twelve knobs, but don't publish an interaction from it. Fold it over first.
A foldover, rerunning the design with every sign reversed, lifts a resolution III design to IV and frees the main effects from two-factor interactions.
Also heard as
- design resolution
- Res III
- Res IV
- Res V
Related terms
Aliasing
Situation in a fractional design where two or more effects leave identical patterns in the data and cannot be told apart.
Fractional factorial design
Experiment that runs a chosen fraction of all factor combinations, trading some aliased effects for far fewer runs.
Interaction
Situation where the effect of one factor depends on the level of another, so their combined effect is not simply additive.
DOE
Design of experiments: planning a set of runs that vary several factors at once so their effects can be separated.