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5.
Process Improvement
5.2. Assumptions
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| Polynomial approximation models only work for smoothly varying outputs | In this chapter we restrict
ourselves to the case where the response variable(s) are continuous outputs
denoted as Y.. Over the experimental range, the outputs must not
only be continuous, but also reasonably smooth. A sharp falloff in Y
values is likely to be missed by the approximating polynomials that we
use because these polynomials assume a smoothly curving underlying response
surface.
If the surface under investigation is known to be only piece wise smooth, then the experiments will have to be broken up into separate experiments, each investigating the shape of the separate sections. A surface that is known to be very jagged (i.e. non smooth) will not be successfully approximated by a smooth polynomial.
Smooth and Jagged Responses |
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