Human inspection errors. Tests of product quality using human inspectors can lead to serious inspection error problems. To evaluate the performance of inspectors in a new company, a quality manager had a sample of 12 novice inspectors evaluate 200 finished products. The same 200 items were evaluated by 12 experienced inspectors. The quality of each item-whether defective or nondefective-was known to the manager. The next table lists the number of inspection errors (classifying a defective item as nondefective or vice versa) made by each inspector. A SAS printout comparing the two types of inspectors is shown in the next column.
(a) Prior to conducting this experiment, the manager believed the variance in inspection errors was lower for experienced inspectors than for novice inspectors. Do the sample data support her belief? Test using α = .05.
(b) What is the appropriate p-value of the test you conducted in part a?
| Novice Inspectors |
Experienced Inspectors |
| 30 |
35 |
26 |
40 |
31 |
15 |
25 |
19 |
| 36 |
20 |
45 |
31 |
28 |
17 |
19 |
18 |
| 33 |
29 |
21 |
48 |
24 |
10 |
20 |
21 |