A utility function that is used to summarize the objectives of a response surface analysis into a single equation. When the analysis involves multiple response variables, each is assigned an individual desirability value, d(i), between 0 (least desirable) and 1 (most desirable). The overall desirability (D) is the geometric mean of the individual desirability functions, which is then optimized using numerical methods.
Graphs of the overall disability for specific levels of one input variable while holding all others constant are then compared to help find the optimal input parameter settings that satisfy all the response surface objectives.
More on Desirability Functions from NIST: - http://www.itl.nist.gov/div898/handbook/pri/section5/pri5322.htm Desirability Functions from StatEase Inc.: - http://www.statease.com/pubs/derringer.pdf