A response optimization plot was drawn to identify the factor settings that optimize a single response or a set of responses. This is useful in determining the operating conditions that will result in a desirable response. The optimum conditions, which are defined as the best combination of factor settings for achieving the optimum
response, were a temperature of 20.0 8C and a pH of 8.99 for a predicted response of absorbance of 0.90 and a desirability score of 0.99 (Fig. 8). There are many other advantages of using optimization plots, i.e., to achieve a predicted response with a higher desirability score; to lower cost factor settings with nearoptimum properties; to study the sensitivity of response variables; to change factor settings; and to obtain the required response factor setting of interest.