and one product. Surfaces can be represented either
graphically or mathematically in generalized form.
Mathematically, yield (Y) is a function of the quantity
of input (X), that is Y = f (X).
 The simplest form of a response surface, one that is
seldom useful, is a straight line (Fig. VI-la).
Generally, linear responses are found only with small
changes in the level of the input.


Product











Product


Product


 Linear



 Input

 1c.



Square Root




 Input


Product


Product


 lb.


Quadratic





 Input


 1d.



 Cubic




 Input


 le.



Logarithmic




Input


FIG.VI-1. Two-dimensional response surfaces.