ABSTRACT
This chapter describes iterative strategies which are useful for solving empirical problems. The use of such strategies is particularly effective when a series of small experiments is used to solve a complex problem. A good approach for qualitative variables is to look at all the samples at the same time and order them according to the qualitative response. Factors such as time, temperature, concentration, etc. are continuous variables. Qualitative variables such as type of buffer salts, type of antigen, etc., are easy to use as long as people are willing to consider only two or three values or levels at a time in a single experiment. In addition to process variables, experimental factors might include the following: raw materials, lab technician, supplier of antigen or reagent, etc. An important experimental factor which has been left out of an experimental design is sometimes called a lurking variable.
