Resolution

Resolution is a measure of the degree of confounding in an experimental design. A factor or factor interaction is said to be confounded (or aliased) with another when the individual effects of the factors or factor interactions cannot be separated one from the other because of the limitations of the experimental data. In a complete factorial design there is no confounding.

Resolution III: At least one main factor may be confounded with an interaction. Used only for screening experiments

Resolution IV: At least two 2-factor interactions may be confounded with one another. No main factors are confounded with 2-factor interactions. Main factors may be confounded with 3-factor interactions.

Resolution V: No main or 2-factor interactions are confounded with one another. Two-factor interactions may be confounded with 3-factor.

Resolution VI: No main or 2-factor or 3-factor interactions are confounded with one another. Three-factor interactions may be confounded with one another.

Mixture designs are constructed to satisfy a "limited resolution" which requires only linear interactions.

Resolution as a way of describing performance of a design is most useful when complete sets of interactions are required. Generally, a design for some sub-set of the complete interaction set will be smaller than one for the complete set. Confounding may be found in experimental arrays with missing data or added factors.

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