7.2 Consider a CRD with 5 treatments, 6 replications for each treatment and 4 obser- vations for every experimental unit. Suppose the treatments represent increasing amounts (x) of fertilizer applied to a certain crop. The following (partial) results are obtained:

Using the method of orthogonal polynomials investigate whether (i) the data exhibit linear and quadratic trends; (ii) first and second order terms provide an adequate fit to the data.

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xj 0 2 4 6 8 Ji.. 4.9 10.0 13.9 15.7 16.3 SS(EE) 50.0, SS(OE) = 60.0