A special type of design of experiments is Response surface
methodology (RSM). RSM includes a group of statistical methods
for model development and employment. These methods search to
relate a response (output variable) to a number of affecting factors
(input variables), via an accurate design and investigation of experiments.
It permits designs to be made of the response at intermediate
levels which were not experimentally investigated and
indicates how the response can be optimized (Abbasi et al., 1987).
RSM by means of Box Behnken (Box and Draper, 1987) design was
employed to optimize the response of five input variables. The
optimization process comprises studying the response of the statistically
planned combinations, optimizing coefficients, predicting
the response of the fitted model and testing the accuracy of the
model. Implementation of response surface method (RSM) in process
optimization is very common; especially when the type of the