ABSTRACT
By deploying a mixture design that provides adequate models for critical attributes formulators often discover a region where components combine to meet all specifications. This is known as the “sweet spot.” A simple, yet effective, way to gauge when one hit this spot for multiple responses is by scaling them all to one objective function called “desirability.” Being on a roll with paint, let’s see how desirability works by way of a case study from the coatings industry. When every goal is at least minimally met, that is, just inside the lower and or threshold level, an overall desirability above zero is achieved. The chapter illustrates the application of the confidence interval (CI) and, ultimately the tolerance interval (TI), to achieve a Quality by Design (QbD) space. To develop assurance for the quality of their products, manufacturers must back off from their specification boundary by the CI, or, more conservatively for QbD, the TI.
