Design resolution is simply described by the effects in fractional factorial design with other effects. When doing fractional factorial design, there are several effects that are confounded. In other words, they can’t be separately estimated from each.
In most cases, you want to make use of fractional factorial design with highest resolution possible for the required amount of fractionation.
To give you an example, it is preferable to pick design in which the primary effects are cofounded with Resolution IV (3-way interaction) rather than a design in which main effects are Resolution III (2-way interactions).
Common Denominator of Resolution V, IV & III
- Resolution III – no main effects aliased w/ other main effect. The main effects though are aliased with a 2-factor interaction.
- Resolution IV – in this regard, much like the Resolution III, there are no main effects being aliased with other main effect or in 2 factor interactions. However, some of the 2-factor interaction are being aliased with the other 2-factor interaction. Not only that, the main effects are being aliased with a 3-factor interaction.
- Resolution V – for this one, no main effects or even 2-factor interaction are being aliased with other main effects or 2-factor interactions. The thing is, 2-factor interactions are being aliased with 3-factor interaction and the main effects are often aliased with a 4-factor interaction.