Data for	X and R	bar charts
n = 4
Sample #			Measurements		X-bar	R
1	12.2	12.5	11.0	11.9	11.90	1.50
2	11.5	12.1	11.9	12.1	11.90	0.60
3	12.6	12.8	13.2	12.4	12.75	0.80
4	11.9	13.6	13.9	13.2	13.15	2.00
5	10.8	11.8	12.7	11.1	11.60	1.90
6	12.6	11.1	12.1	12.9	12.18	1.80
7	13.0	12.8	12.8	11.6	12.55	1.40
8	12.5	12.3	12.3	10.7	11.95	1.80
9	11.0	11.0	12.4	12.8	11.80	1.80
10	11.3	11.2	11.3	12.2	11.50	1.00
11	12.6	11.9	11.4	12.5	12.10	1.20
12	11.9	12.5	12.1	11.1	11.90	1.40
13	13.1	12.5	13.5	12.1	12.80	1.40
14	12.6	13.3	12.2	10.5	12.15	2.10
15	12.6	11.0	11.1	9.7	11.10	2.90
Totals					181.33	23.60
					12.09	1.57

find the upper and lower limits