7. The following table lists all costs of quality incurred by Sam’s Surf Shop last year. What
was Sam’s appraisal cost for quality last year?
Annual inspection costs $ 155,000
Annual cost of scrap materials 286,000
Annual rework cost 34,679
Annual cost of quality training 456,000
Annual warranty cost 1,546,000
Annual testing cost 543,000
10. A manufacturing company has been inspecting units of output from a process. Each product
inspected is evaluated on fi ve criteria. If the unit does not meet standards for the criteria
it counts as a defect for the unit. Each unit could have as few as zero defects, and as
many as fi ve. After inspecting 2,000 units, they discovered 33 defects. What is the DPMO
measure for this process?
6. C-Spec, Inc., is attempting to determine whether an existing machine is capable of milling
an engine part that has a key specifi cation of 4 6 .003 inches. After a trial run on this
machine, C-Spec has determined that the machine has a sample mean of 4.001 inches
with a standard deviation of .002 inch.
a. Calculate the Cpk for this machine.
b. Should C-Spec use this machine to produce this part? Why?
7. Ten samples of 15 parts each were taken from an ongoing process to establish a p-chart
for control. The samples and the number of defectives in each are shown in the following
table:
a. Develop a p-chart for 95 percent confi dence (1.96 standard deviation).
b. Based on the plotted data points, what comments can you make?
8. A shirt manufacturer buys cloth by the 100-yard roll from a supplier. For setting up a
control chart to manage the irregularities (e.g., loose threads and tears), the following data
were collected from a sample provided by the supplier.
Sample 1 2 3 4 5 6 7 8 9 1 0
Irregularities 3 5 2 6 5 4 6 3 4 5
a. Using these data, set up a c-chart with z 5 2.
b. Suppose the next fi ve rolls from the supplier had three, two, fi ve, three, and seven irregularities.
Is the supplier process under control?
9. Resistors for electronic circuits are manufactured on a high-speed automated machine.
The machine is set up to produce a large run of resistors of 1,000 ohms each.
To set up the machine and to create a control chart to be used throughout the run,
15 samples were taken with four resistors in each sample. The complete list of samples
and their measured values are as follows:
Develop an
__
X – chart and an R-chart and plot the values. From the charts, what comments
can you make about the process? (Use three-sigma control limits as in Exhibit 13.7.)
