(a) A 3 x 3 factorial design was used to explore the effects of three sources of clay I, II, III and three ceramic molds A, B, C. Five replicates of each clay-mold combination were prepared and all 45 randomly placed within a furnace before firing. The response is a measure of surface roughness:
Might a transformation be useful for these data? Why?
(b) Make calculations to show if an appropriate transformation might change the interpretation of these data.