This talk deals with thorny issues that confront every experimenter: How to handle results that fit badly with your chosen model. Design-Expert software provides graphical tools that make it easy to diagnose what is wrong—damaging outliers and/or a need for transformation. A variety of case studies will demonstrate the value of these diagnostics. They make save you a great deal of embarrassment for incorrect interpretation of experimental results, or the opportunity lost by letting bad data obscure a breakthrough discovery.