Variants of split-plot designs

Adaptations of the split-plot methodology have been suggested by many authors (see, for example, Kempthome [18], Cochran and Cox [44]). These authors describe various blocking arrangements to control for other sources of variation in split-plot experiments. The relevance of some of these arrangements to split-plot designs that investigate the influence of environmental variation is discussed in Box and Jones [5]. 

The use of factorial and fractional factorial designs in split-plot arrangements has been investigated by Addelman [46], see also Daniel [47]. As an example of such an arrangement, consider a tablet formulation experiment with two environmental variables, temperature (T) and humidity (H), and five design variables. A, B, C, D, and E with all of the 

An alternative design would be to use a half-fraction of the design variables for each run of the chamber. Such a design, before randomization, is shown in Table 2.22. With this design the ABCDE five-factor interaction is confounded with the TxH whole-plot contrast. Under the assumption of negligible three-factor and higher-order interactions all main effects and two-factor interactions can be estimated as well as interactions between the design and the environmental variables. 

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