Confounding effects in fractional factorial designs

Examination of the main effect of factor D reveals that it is identical to this main effect. This can be done for all two factor interaction effects to reveal the confounding pattern shown in Table 5.13. 

THE CONFOUNDING PATTERN FOR THE PLACKET-BURMAN DESIGN SHOWN IN TABLE 5.9 

An awareness of these confounding effects can help both in the design of a ruggedness study and in the interpretation of results. For instance, factors that are considered likely to interact can be placed such that they overwrite the dummy effect, thus removing them from altering other main effects and allowing a possible identification of the effect. If a factor is observed to have an effect that cannot be attributed to that factor, e.g. an 

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