From Factorial to Sequential Designs

In environmental analysis we shall extremely seldom expect questions to be answered by methods of sequential design. It could, however, be possible that one is, for example, asked to locate the maximum contamination within a certain area, so that the decontamination process can start there. In the following discussion we will, therefore, provide only a brief summary of some optimization methods which could be useful. 

In order to link the section on exactly planned experiments and the section on pure sequential methods let us roughly describe the method of BOX and WILSON [1951] with two factors under study. 

If the borders of the experimental space are reached, for example a river parallel to road no. 1, it is normally sufficient to set-up a first order polynomial there and to follow the possibly changed direction of its gradient. Remember that the gradient of a first order polynomial is simply constructed from the linear coefficients of the polynomial. 

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