The time to replace vehicle wiper blades at a service
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Posted on: 06/18/2016 02:08 AM Due on: 06/18/2016
SPC Homework Problems
1. The time to replace vehicle wiper blades at a service center was monitored using a mean and a
range chart. Six samples of n=20 observations were obtained and the sample means and ranges
computed:
Sample
1
2
3
4
5
6
Mean
3.06
3.15
3.11
3.13
3.06
3.09
Range
.42
.50
.41
.46
.46
.45
a. Using the factors in Table S6.1, determine upper and lower limits for mean and range charts.
Range for true population is lower is 3.070 and upper is 3.130
And its same for range in the confidence interval percentage of 90.
b. Is the process in control?
c. Yes its in control because the mean is not with the range of any outlier.
2. Each of the processes listed is noncentered with respect to the specifications for that process.
Compute the appropriate capability index for each, and decide if the process is capable.
Process
Mean
H
K
T
15.0
33.0
18.5
Standard
Deviation
0.32
1.00
0.40
Lower Spec
Upper Spec
14.1
30.0
16.5
16.0
36.5
20.1
3. pchart and cchart. Using the appropriate control chart, determine threesigma control limits
for each case:
a. An inspector found an average of 3.9 scratches in the exterior paint of each of the
automobiles being prepared for shipment to dealers.
b. Before shipping lawn mowers to dealers, an inspector attempts to start each mower and
notes any that do not start on the first try. The lot size is 100 mowers, and an average of 4
did not start (4 percent).
SPC Homework Problems
1. The time to replace vehicle wiper blades at a service center was monitored using a mean and a
range chart. Six samples of n=20 observations were obtained and the sample means and ranges
computed:
Sample
1
2
3
4
5
6
Mean
3.06
3.15
3.11
3.13
3.06
3.09
Range
.42
.50
.41
.46
.46
.45
a. Using the factors in Table S6.1, determine upper and lower limits for mean and range charts.
Range for true population is lower is 3.070 and upper is 3.130
And its same for range in the confidence interval percentage of 90.
b. Is the process in control?
c. Yes its in control because the mean is not with the range of any outlier.
2. Each of the processes listed is noncentered with respect to the specifications for that process.
Compute the appropriate capability index for each, and decide if the process is capable.
Process
Mean
H
K
T
15.0
33.0
18.5
Standard
Deviation
0.32
1.00
0.40
Lower Spec
Upper Spec
14.1
30.0
16.5
16.0
36.5
20.1
3. pchart and cchart. Using the appropriate control chart, determine threesigma control limits
for each case:
a. An inspector found an average of 3.9 scratches in the exterior paint of each of the
automobiles being prepared for shipment to dealers.
b. Before shipping lawn mowers to dealers, an inspector attempts to start each mower and
notes any that do not start on the first try. The lot size is 100 mowers, and an average of 4
did not start (4 percent).
SPC Homework Problems

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The time to replace vehicle wiper blades at a service