Fractional factorial designs problem

The examination of more than one of the non-procedure related factors (e.g. different laboratories, analysts, instruments, columns or batches of reagents, days) by Plackett-Burman and fractional factorial designs causes problems. These designs require combinations that are impossible to... 

Problem 2.2 Use of a Fractional Factorial Design to Study Factors That Influence NO Emissions in a Combustor... 

There are 8 coefficients in the model. The design must therefore contain not less than 8 experiments. Is it possible to constmct a fractional factorial design of only 8 (2 ) experiments allowing the resolution of the problem ... 

In general, whenever one is faced with a blocking issue with known variables, then the problem can be reduced and analysed as if it were a fractional factorial design with additional dummy variables. In this particular example, let the original factors be A, B, C, and D and let the blocking variable be an additional fifth factor, E. Since we have been told that the AB interaction is zero, in order to minimise the confounding, let E = AB. All runs... 

When some of the possible data points are omitted in factorial designs they are known as fractionally or partially replicated designs. The choice of points to be omitted is of considerable importance. There is no single fractional replicate which is best for any given complete factorial design. Usually the experimenter will have some idea as to the expected effects. When this sort of intuition is available, a particular design may be developed to fit a particular problem. 

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