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xviii List of Figures and Tables
Figure 19.1 Flowchart of a process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
Table 19.1
Check sheet summarizing the data of a study over a period of
four weeks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
Figure 19.2 An initial form of a cause-and-effect diagram. . . . . . . . . . . . . . . . . . . . . . . . . 250
Figure 19.3 A completed cause-and-effect diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
Figure 19.4 A damaged item shaped as a rectangular prism. . . . . . . . . . . . . . . . . . . . . . . 251
Table 19.2 Percentage of nonconforming units in 30 different shifts. . . . . . . . . . . . . . . 252
Figure 19.5 Run chart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
Figure 19.6 A pictorial representation of the components of a control chart. . . . . . . . . . 253
Figure 19.7 OC curves for the X – chart with three-sigma limits, for different
sample sizes n. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
Table 19.3 Diameter measurements (mm) of ball bearings used in the wheels of
heavy construction equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
Figure 19.8 X – and R control chart for the ball bearing data in Table 19.3. . . . . . . . . . . . . 267
Figure 19.9 The X – and S control chart for the ball bearing data in Table 19.3. . . . . . . . . 273
Table 19.4 Control charts for attributes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
Table 19.5 Number of nonconforming computer chips out of 1000 inspected
each day during the study period of 30 days. . . . . . . . . . . . . . . . . . . . . . . . . . 279
Figure 19.10 p chart for nonconforming computer chips, using trial control limits
for the data in Table 19.5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
Table 19.6 Number of nonconforming computer chips with different size
samples inspected each day during the study period of 30 days. . . . . . . . . 282
Figure 19.11 p chart for nonconforming chips with variable sample sizes, using
trial control limits for the data in Table 19.6. . . . . . . . . . . . . . . . . . . . . . . . . . . 283
Figure 19.12 np chart for nonconforming computer chips, using trial control limits
for the data in Table 19.5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
Table 19.7 Total number of nonconformities in samples of five rolls of paper. . . . . . . . 287
Figure 19.13 c control chart of nonconformities for the data in Table 19.7. . . . . . . . . . . . . 287
Table 19.8 Number of nonconformities on printed boards for laptops per
sample; each sample consists of five inspection units. . . . . . . . . . . . . . . . . . . 290
Figure 19.14 u chart of nonconformities for the data in Table 19.8. . . . . . . . . . . . . . . . . . . . 291
Table 19.9 Number of nonconformities on printed boards for laptops per sample,
with varying sample size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
Figure 19.15 u chart of nonconformities for the data in Table 19.9. . . . . . . . . . . . . . . . . . . . 293
Table 19.10 Data showing the lengths of tie rods for cars. . . . . . . . . . . . . . . . . . . . . . . . . . 298
Table 19.11 Different processes with the same value of C pk . . . . . . . . . . . . . . . . . . . . . . . . 301
Table 19.12 Parts per million of nonconforming units for different values of C pk . . . . . . 301
Table 20.1 Audit types and scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
Figure 21.1 Plan–do–check–act cycle.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317