In: Operations Management
Webster Chemical Company produces mastics and caulking for the construction industry. The product is blended in large mixers and then pumped into tubes and capped. Management is concerned about whether the filling process for tubes of caulking is in statistical control. The process should be centered on 8 ounces per tube. Several samples of eight tubes were taken, each tube was weighed, and the weights in the table below were obtained.
the ounces of caulking per tube data.
Tube number |
||||||||
Sample |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
1 |
7.58 |
8.34 |
8.02 |
7.94 |
8.44 |
7.67 |
7.81 |
8.11 |
2 |
8.33 |
8.17 |
8.08 |
8.51 |
8.41 |
8.28 |
8.09 |
8.16 |
3 |
7.89 |
7.77 |
7.81 |
8.04 |
8.00 |
7.89 |
7.93 |
8.09 |
4 |
8.24 |
8.18 |
7.83 |
8.03 |
7.90 |
8.16 |
7.97 |
8.07 |
5 |
7.87 |
8.13 |
7.92 |
7.99 |
7.94 |
7.81 |
8.14 |
7.88 |
6 |
8.13 |
8.14 |
8.11 |
8.13 |
8.14 |
7.99 |
8.13 |
8.14 |
the table of factors for calculating three-sigma limits for the x over bar x-chart and R-chart.
Factors for calculating three-sigma limits for the
x overbarx-chart
and R-chart.
Size of Sample (n) |
Factor for UCL and LCL for
x overbarx-chart (Upper A 2A2) |
Factor for LCL for R-Chart
(Upper D 3D3) |
Factor for UCL for R-Chart
(Upper D 4D4) |
2 |
1.880 |
0 |
3.267 |
3 |
1.023 |
0 |
2.575 |
4 |
0.729 |
0 |
2.282 |
5 |
0.577 |
0 |
2.115 |
6 |
0.483 |
0 |
2.004 |
7 |
0.419 |
0.076 |
1.924 |
8 |
0.373 |
0.136 |
1.864 |
9 |
0.337 |
0.184 |
1.816 |
10 |
0.308 |
0.223 |
1.777 |
a. Assume that only six samples are sufficient and develop the control charts for the mean and the range.
Set up the R-chart by specifying the center line and three-sigma control limits below. (Enter your responses rounded to three decimal places.)
R-chart |
||
UCL Subscript Upper RUCLR |
equals= |
|
Upper R overbarR |
equals= |
|
LCL Subscript Upper RLCLR |
equals= |
# SAMPLE |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
AVERAGE |
RANGE |
1 |
7.58 |
8.34 |
8.02 |
7.94 |
8.44 |
7.67 |
7.81 |
8.11 |
7.99 |
0.86 |
2 |
8.33 |
8.17 |
8.08 |
8.51 |
8.41 |
8.28 |
8.09 |
8.16 |
8.25 |
0.43 |
3 |
7.89 |
7.77 |
7.81 |
8.04 |
8 |
7.89 |
7.93 |
8.09 |
7.93 |
0.32 |
4 |
8.24 |
8.18 |
7.83 |
8.03 |
7.9 |
8.16 |
7.97 |
8.07 |
8.05 |
0.41 |
5 |
7.87 |
8.13 |
7.92 |
7.99 |
7.94 |
7.81 |
8.14 |
7.88 |
7.96 |
0.33 |
6 |
8.13 |
8.14 |
8.11 |
8.13 |
8.14 |
7.99 |
8.13 |
8.14 |
8.11 |
0.15 |
AVERAGE |
8.05 |
0.42 |
RANGE = LARGEST OBSERVATION - SMALLEST OBSERVATION
XBAR = 8.05
RBAR = 0.42
A2 VALUE CORRESPONDING TO N = 8 = 0.373
D3 & D4 VALUES CORRESPONDING TO N = 8 = 0.136, 1.864
CONTROL LIMITS FOR XBAR
UCL X = XBAR + (A2 * RBAR) = 8.05 + (0.373 * 0.42) = 8.21
LCL X = XBAR - (A2 * RBAR) = 8.05 - (0.373 * 0.42) = 7.89
NO, BECAUSE ONE OR MORE POINTS ARE ABOVE THE UCL
CONTROL LIMITS FOR RBAR
UCL R = RBAR * D4 = 0.42 * 1.864 = 0.78
LCL R = RBAR * D3 = 0.42 * 0.136 = 0.06
NO, BECAUSE ONE OR MORE POINTS ARE ABOVE THE UCL
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