跪求Pb管制图的计算过程？急！加分！

序号 塑膠Pb
Pb UCL LCL
1 93.2 109.25 80.75
2 93.2 109.25 80.75
3 91.3 109.25 80.75
4 93.6 109.25 80.75
5 93.5 109.25 80.75
6 92.9 109.25 80.75
7 92.5 109.25 80.75
8 93.7 109.25 80.75
9 93.7 109.25 80.75
10 93.7 109.25 80.75
11 92.7 109.25 80.75
12 94.6 109.25 80.75
13 93 109.25 80.75
14 94 109.25 80.75
15 93.5 109.25 80.75
16 93.2 109.25 80.75
17 92.1 109.25 80.75
18 93 109.25 80.75
19 94.9 109.25 80.75
20 93.8 109.25 80.75
21 93.1 109.25 80.75
22 93.4 109.25 80.75
23 94.2 109.25 80.75
24 93.8 109.25 80.75
25 93.9 109.25 80.75
26 92 109.25 80.75
27 91.8 109.25 80.75
28 94.2 109.25 80.75
29 94.7 109.25 80.75
30 92.8 109.25 80.75
31 92.9 109.25 80.75
32 93.9 109.25 80.75
33 93.9 109.25 80.75
34 94.5 109.25 80.75
35 92.8 109.25 80.75
36 94 109.25 80.75
37 94.1 109.25 80.75
38 95.1 109.25 80.75
39 92.1 109.25 80.75
40 91.4 109.25 80.75
41 94 109.25 80.75
42 93 109.25 80.75
43 94.8 109.25 80.75
44 93.4 109.25 80.75
45 96 109.25 80.75
46 95.4 109.25 80.75
47 95.5 109.25 80.75
48 94.1 109.25 80.75
49 92 109.25 80.75
50 94.7 109.25 80.75
51 95.2 109.25 80.75
52 95.2 109.25 80.75
53 95.5 109.25 80.75
54 93.8 109.25 80.75
55 94.6 109.25 80.75
56 95.8 109.25 80.75
57 92.4 109.25 80.75
58 94 109.25 80.75
59 95.1 109.25 80.75
60 94.2 109.25 80.75
MAX 96
MIN 91.3
请各位大是指教一下，这组数的中心线、上限、下限值计算过程是怎么样的？加分啊！