Suppose that a chemical engineer is interested in the effect of catalyst feed rate on the viscosity of a polymer. She knows that there are several factors, such as raw material source, temperature, operator, and raw material purity that are very difficult to control in the full-scale process. Therefore she decides to test the catalyst feed rate factor in blocks, where each blocks consist of some combination of these uncontrollable factor. In effect, she is using the blocks to test the robustness of her process variable (feed rate) to conditions she cannot easily control. Suppose that the experiment was conducted as described and that the following Rockwell C-scale data (coded by subtracting 40 units) obtained