Cover cases for a personal computer are manufactured by injection molding. Samples of five cases are taken from the process periodically, and the number of defects is noted. Twenty-five samples follow:

(a) Using all the data, find trial control limits for a U chart for the process.

(b) Use the trial control limits from part (a) to identify out-of-control points. If necessary, revise your control limits.

(c) Suppose that instead of samples of five cases, the sample size was 10. Repeat parts (a) and (b). Explain how this change alters your responses to parts (a) and (b).

No. of Defects Sample No. of Defects Sample 1 14 2 15 16 3 2 4 1 17 4 5 18 3 3 19 5 2 20 4 21 1 22 10 23 9. 11 2 24 3 12 3 25 2 13 2