Question

Below are X-bar and R values for 12 samples of size = 5. They are taken from a process producing bearings. The measurements are made on the inside diameter of the bearing. The data have been coded from 0.50; in other words, a measurement of 0.50345 has been recorded as 345. Range values are coded from 0.000; that is, 0.00013 is recorded as 13.

Subgroup Number	X-bar	Range
1	145	13
2	147	14
3	150	12
4	146	11
5	150	15
6	145	16
7	149	14
8	148	13
9	148	12
10	154	15
11	152	13
12	155	16

Set up the X-bar and R charts on this process. Does the process seem to be in control? Why or why not? If necessary, assume assignable cause and revise the trial control limits.

Answer 1