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Chapter 19: B. Statistical Process Control 293
Continued
u Chart
15.0
UCL = 14.48
Sample count per unit
12.5
10.0
7.5
u – = 9.22
5.0
3 6 9 12 15 18 21 24 27 30
Sample
Tests performed with unequal sample sizes
LCL = 3.96
Figure 19.15 u chart of nonconformities for the data in Table 19.9.
5. PROCESS CAPABILITY ANALYSIS
Process capability analysis. Define and
distinguish between C p , C pk , P p , and
P pk and apply them to various data sets.
(Application)
Part IV.B.5
Body of Knowledge IV.B.5
Earlier in this chapter we defined what a process is. Once a process is defined and
brought under statistical control, the next concern of a manufacturer is to ensure
that he or she can deliver the product that the consumer wants. In other words,
he or she would want to determine whether the process is capable of delivering
the desired product. One way to address such a concern is to quantify the capability.
A process capability index (PCI) is a unitless measure that quantifies the process
capability, specifically the relationship between the output and the designed tolerances.
This measure has become an important tool in process capability analysis.
Moreover, since the process capability index is a unitless measure of capability,
it has become an easy tool of communication between the manufacturer and the