ABSTRACT
This chapter provides designs that combine varying compositions of mixtures with changes in levels of process factors and other variables. The frosting on the cake, perhaps literally, is to experiment on two mixtures simultaneously, that is, a “mix–mix.” The combined designs unlock a universe of potential synergisms. The chapter begins with the simplest combined experiment—one that incorporates a single process factor. A standard mixture experiment assumes that the response depends only on the proportions of the components present, for example, when tasting the food, a nibble will do. The chapter illustrates the structure of “mixture-amount” design (MAD) and modeling of results via a case study on a controlled-release ibuprofen tablet. To illustrate how to set up such a combined design, the chapter looks at a hypothetical case on the material science of a composite material used in aerospace. In composites, one material, such as epoxy resin, serves as a “matrix” to hold everything together.
