Experiments at three levels first-order model

3 Experiments at three levels first-order model 

For this section, we will assume the model y = Po + Pi, + We will examine the (AT AT) matrix to determine the effect of carrying out a third experiment between x, = -5 and x, = +5 given the very special case of two fixed experiments located at x, = +1 and x,2 = -1 (see Chapter 7 and Example 7.4). We give four numerical examples of the calculation of the (X X) matrix, one each for x,3 = -4, 0, +0.5, and +4. 

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