An automobile manufacturer wishes to control the number of nonconformities in a subassembly area producing manual transmissions. The inspection unit is defined as four transmissions, and data from 16 samples (each of size 4) are shown in Table 6E.13.

a. Set up a control chart for nonconformities per unit.
b. Do these data come from a controlled process? If not, assume that assignable causes can be found for all out-of-control points and calculate the revised control chart parameters.
c. Suppose the inspection unit is redefined as eight transmissions. Design an appropriate control chart for monitoring future production.

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Sample Number of SampleNumber of Number Nonconformities Number Nonconformities 10 12 13 14 15 16