ABSTRACT
This chapter demonstrates how to recognize a nested factor. It shows how a nested factor is denoted and its effect on the mathematical model and associated tests. For factorial designs, one generate the mathematical model by forming all possible interactions and combining the subscripts for each interaction. The same procedure is used for nested factors except a nested factor cannot interact with any factor(s) it is nested within. This is because the nested factor has different levels for each level of the factor it is nested within so there is no basis for computing an interaction. Sometimes factors will appear to be nested when they are not meant to be. This can happen when, for example, the low and high values of one factor depend on the level of another factor, either from some known scientific principle or because the second factor implies different parts must be used.
