Atlas Copco Power Focus 3000 - Constants for calculation of SPC variables

Statistic
280 (428) 9836 3123 01
32
,DA
and
4
D
are tabular constants and depend on the subgroup size.
19.6 Constants for calculation of SPC variables
Sub group
size
Divisors for
estimation of
standard div.
Factors for control limits
N
D
2
C
4
A
2
D
3
D
4
A
3
B
3
B
4
2
1.13
0.798
1.88
-
3.27
2.66
-
3.27
3
1.69
0.886
1.02
-
2.57
1.95
-
2.57
4
2.06
0.921
0.73
-
2.28
1.63
-
2.27
5
2.33
0.940
0.58
-
2.11
1.43
-
2.09
6
2.53
0.952
0.48
-
2.00
1.29
0.03
1.97
7
2.70
0.959
0.42
0.08
1.92
1.18
0.12
1.88
8
2.85
0.965
0.37
0.14
1.86
1.10
0.19
1.82
9
2.97
0.969
0.34
0.18
1.82
1.03
0.24
1.76
10
3.08
0.973
0.31
0.22
1.78
0.98
0.28
1.72
11
3.17
0.975
0.29
0.26
1.74
0.93
0.32
1.68
12
3.26
0.978
0.27
0.28
1.72
0.89
0.35
1.65
13
3.34
0.979
0.25
0.31
1.69
0.85
0.38
1.62
14
3.41
0.981
0.24
0.33
1.67
0.82
0.41
1.59
15
3.47
0.982
0.22
0.35
1.65
0.79
0.43
1.57
16
3.53
0.984
0.21
0.36
1.63
0.76
0.45
1.55
17
3.59
0.985
0.20
0.38
1.62
0.74
0.47
1.53
18
3.64
0.985
0.19
0.39
1.61
0.72
0.48
1.52
19
3.69
0.986
0.19
0.40
1.60
0.69
0.50
1.50
20
3.74
0.987
0.18
0.42
1.59
0.68
0.51
1.49
21
3.78
0.988
0.17
0.42
1.58
0.66
0.52
1.48
22
3.82
0.988
0.17
0.43
1.57
0.65
0.53
1.47
23
3.86
0.989
0.16
0.44
1.56
0.63
0.55
1.46
24
3.90
0.989
0.16
0.45
1.55
0.62
0.56
1.45
25
3.93
0.990
0.15
0.46
1.54
0.61
0.57
1.44