过程均值 X=(X1+X2+......+Xn)/n
=(6.84+6.86+......+6.92)/25
=6.8784
平均极差 R=(R1+R2+......+Rn)/n
=(0.3*6+0.2*17+0.1*2)/25
=0.216
Uclx = X+A2R = 6.8784+0.58*0.216 = 7.0037
Lclx = X-A2R = 6.8784-0.58*0.216 = 6.7531
Uclr = D4R = 2.11*0.216 = 0.4558
Lclr = D3R = 0*0.216 = 0
式中A2,D3,D4为常系数,决定于子组样本容量。
1其系数值见下表 :
n | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
D4 | 3.27 | 2.57 | 2.28 | 2.11 | 2.00 | 1.92 | 1.86 | 1.82 | 1.78 |
D3 | ٭ | ٭ | ٭ | ٭ | ٭ | 0.08 | 0.14 | 0.18 | 0.22 |
A2 | 1.88 | 1.02 | 0.73 | 0.58 | 0.48 | 0.42 | 0.34 | 0.34 | 0.31 |