Table 1 Statistical Process Control (SPC) Problem Data* Sample Observation Numbe
ID: 446606 • Letter: T
Question
Table 1 Statistical Process Control (SPC) Problem Data*
Sample
Observation Number
Observation Number
Observation Number
Number
1
2
3
Row Average
Row Range
1
10.1
10.6
9.6
10.1
1.00
2
9.7
9.4
9.0
9.37
0.70
3
10.1
9.1
10.3
9.83
1.20
4
10.1
10.3
10.9
10.43
0.80
5
10.2
9.8
9.0
9.67
1.20
6
10.6
10.2
9.5
10.10
1.10
7
9.5
10.2
10.2
9.97
0.70
*The range and row average help you avoid simple math errors and quicken the time to complete the SPC analysis but you have to know what to use when.
Given the previous results and analysis for the R-chart, one would:
conclude that the R-chart is not in statistical control and proceed to develop the x-bar chart.
plot the x-bar sample means first to see if they are randomly distributed.
conclude that the R-chart is in statistical control and proceed to develop the x-bar chart.
investigate sample # 3 as it is outside the R-chart control limits and redo the R-chart.
Sample
Observation Number
Observation Number
Observation Number
Number
1
2
3
Row Average
Row Range
1
10.1
10.6
9.6
10.1
1.00
2
9.7
9.4
9.0
9.37
0.70
3
10.1
9.1
10.3
9.83
1.20
4
10.1
10.3
10.9
10.43
0.80
5
10.2
9.8
9.0
9.67
1.20
6
10.6
10.2
9.5
10.10
1.10
7
9.5
10.2
10.2
9.97
0.70
Explanation / Answer
c.
conclude that the R-chart is in statistical control and proceed to develop the x-bar chart.
Rm=Mean R=0.957 (sum of all range values / number of observations)=6.7 / 7=0.957
UCL=D4Rm=1.92*0.957=1.84
LCL=D3Rm=0.08*0.957=0.076
all the values in range mean are between 0.076 to 1.84 hence R chart is in statistical control and it's time to proceed to x-bar chart
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