Introduction to Probability and Statistics for Engineers and Scientists

Problems 577

Sample Number of Sample Number of

Number Defectives Number Defectives

1511 4

221210

3113 0

4514 8

5915 3

6416 6

7317 2

8318 1

9219 6

1052010

Does it appear that the process was in control throughout? If not, determine revised

control limits if possible.

13.The following data represent the results of inspecting all personal computers

produced at a given plant during the last 12 days.

Day Number of Units Number Defective

180 5

2 110 7

390 4

480 9

5 100 12

690 10

780 4

870 3

980 5

10 90 6

11 90 5

12 110 7

Does the process appear to have been in control? Determine control limits for

future production.

14.Suppose that when a process is in control each item will be defective with probabil-

ity .04. Suppose that your control chart calls for taking daily samples of size 500.

What is the probability that, if the probability of a defective item should suddenly

shift to .08, your control chart would detect this shift on the next sample?

15.The following data represent the number of defective chips produced on the last

15 days: 121, 133, 98, 85, 101, 78, 66, 82, 90, 78, 85, 81, 100, 75, 89. Would