Sample Number Table 7E.11 Data for Exercise 7.39 Number of Nonconformities Sample Number of Number Nonconformities 1 1 9 2 2 3 10 1 10215 34567∞ 8 2 11 0 12 13 14 15 16 21123 CL = ū = = Σu¡ /m = Σxi/n) /m Ui UCL = ū+3√ū/n LCL = ū - 3√√ū/n

An automobile manufacturer wishes to monitor 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 7E.11. a. Set up a control chart for nonconformities per unit. A u chart of average number of nonconformities per unit is appropriate, with n = 4 transmissions in each inspection. 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. Draw x-bar control chart and R chart c. Suppose the inspection unit is redefined as eight transmissions. Design an appropriate control chart for monitoring future production