Question

8. (8 marks) In order to monitor the thickness of a layer of paint on refrigerator appliances, the quality control department measures the paint thickness for twenty samples of five refrigerators each. Control factors table is provided on page 14. The results are presented in Table 8.1 below.

Table 8.1

Subgroup	Mean	Range
1	2.7	2.54	8.1 What are the upper and lower control limits for the range chart? (2 marks)
2	2.8	2.54
3	2.4	2.38
4	2.7	2.56
5	2.8	2.52	LCL = ____________ (2 decimal places)
6	2.6	2.4
7	2.3	2.3	UCL = ____________ (2 decimal places)
8	2.5	2.64
9	2.3	2.42	8.2 Are the ranges of the 20 subgroups in control? (2 marks)
10	2.4	2.36
11	3	3.08
12	2.5	2.56
13	2.8	2.64	8.3 What are the upper and lower control limits for the mean chart? (2 marks)
14	2.4	2.34
15	2	2.48
16	2.1	2.64
17	1.8	2.26	LCL = ____________ (2 decimal places)
18	3.3	2.54
19	3.2	2.72	UCL = ____________ (2 decimal places)
20	2.9	2.36

    8.4 Are the means of the twenty subgroups in control? (2 marks)

Answer 1