Orthogonal polynomials
Let the dependent variable Y be associated with an independent variable x in the form of a polynomial, given by
Equation (A.1) is a convenient curvilinear expression of y as a function of x and is fitted to observed pairs of associated values yT and xT where T = 1, …, n. Suppose that the variable xT progresses by constant intervals. It is then convenient to standardize the x-scale, written as
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