Fat acidity is a measure of flour quality that depends on the kind of flour, how the flour has been treated, and how long the flour is stored. In this experiment there are two types of flour (Patent or First Clear); the flour treatment factor (extraction) has eleven levels, and the flour has been stored for one of six periods (0, 3, 6, 9, 15, or 21 weeks). We observe only one unit for each factor-level combination. The response is fat acidity in mg KOH/100 g flour (data from Nelson 1961). Analyze these data. Of particular interest are the effect of storage time and how that might depend on the other factors.
