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Appendix B: Computer Resources 365
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Figure B.20 Minitab window showing the C Chart dialog box.
EXAMPLE B.17
A Six Sigma Green Belt team in a semiconductor manufacturer found that the printed
circuit boards for laptops have too many nonconformities of several types such as
shorted trace, open trace, cold solder joint, and solder short. In order to monitor nonconformities
in the printed boards for laptops the Six Sigma Green Belt team wants
to set up a u chart. Therefore, they collected some data by selecting samples of five
inspection units, each inspection unit consisting of 30 boards. The data, which are
shown in Table 19.8, page 290, were collected over a period of 30 days.
Solution:
1. Enter all the data (number of nonconformities given in Table 19.8 in
Chapter 19) in column C1 of the Worksheet window. Click on Stat in the
command menu.
2. Select Control Charts in the pull-down menu under the Stat command menu.
3. Select Attributes Charts from the Control Charts command menu.
4. Click on U in the Attributes Charts command menu. The dialog box entitled
U Chart shown in Figure B.21 appears immediately.
5. Enter C1 in the box under Variables.
6. Enter the sample size in the box next to Subgroup Sizes.
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