Question: A tire manufacturing has been concerned about the number of defective tires found recently. In order to evaluate the true magnitude of the problem, a production manager selected ten random samples of twenty units each for inspection. The number of defective tires found in each sample are as follows:

(a) Develop a p-chart with a z = 3.

(b) Suppose that the next four samples selected had 6, 3, 3, and 4 defects. What conclusion can you make?

Sample Number Defective

1 1

2 3

3 2

4 1

5 4

6 1

7 2

8 0

9 3

10 1