RESPONSE SURFACE DESIGNS WITH MINIMUM CHANGES IN THE RUN SEQUENCE

Randomization in run order is a technique commonly employed by the users of response surface designs to avoid biases in the estimates of the effects of interest which might result from a time trend. It is often desirable to execute the observations in an experimental design in such an order that the number of input factor level changes is kept small. Randomizing the run order of a response surface experiment does not always neutralize the effect of undesirable factors. In fact, with some very reasonable assumptions, an important proportion of random orders achieve the same degree of protection as that obtained by experimenting in the standard order. In addition, randomization can induce a large number of changes in factor levels and thus make experimentation expensive and difficult. Here, a methodology to obtain experimentation orders with the desired properties for response surface designs with any number of runs has been discussed.