140 Quality Assurance
The classic SPC model for a generic process is shown in Figure 12.1. The
reader will notice that the product or service goes directly to the customer with-
out any kind of handling. This is what is called the rst time throughput capabil-
ity. Obviously, the product development and production is the PROCESS. We
include product development because that is also a process and it may have
issues with variability as well. The products or services are the outputs of the
process that the customer is willing to pay. That presupposes that all the speci-
cations have been met. The feedback is given by the customer to both inputs
and the process itself, so that improvements may be made as soon as possible.
A much more detailed discussion on this is given by Stamatis (2003).
These four items (inputs, process, outputs, and feedback) are essential in
any endeavor of SPC as they focus on improvement of the process rather
than the product. The emphasis is on the following:
• Describe components of a process
• Document a process
• Describe features/applications of process improvement tools
• Describe the concept of variation
• Identify opportunities for process improvement
• Describe statistical measures of location, dispersion, and skewness
• Assess process performance in terms of capability indices
These items identify a systematic approach that must be managed by man-
agement. The systematic approach is to
• Understand the process from start to nish
• Dene the process goals
• Understand how to achieve the dened goals
• Focus on key elements (indicators) of the process
• Monitor, evaluate, and improve the process
On the other hand, the management approach is a way to dene, develop,
and cascade to the organization the overall strategy of continual improvement.
Classic SPC model.