12.5. Continuation of Problem 12.5. Reconsider the leaf spring experiment from Table 12.1. Suppose that factors A, B and C are controllable variables and that factors D and E are noise factors. Show how a combined array design can be employed to investigate this problem that allows all twofactor interaction to be estimated and only requires 16 runs.

Compare this with the crossed array design from Problem 12.5. Can you see how in general combined array designs have fewer runs than crossed array designs?