Operations Management: An Integrated Approach, 5th Edition

PROCESS CAPABILITY

Process capability

The ability of a production process to meet or exceed preset specifications.

Product specifications

Preset ranges of acceptable quality characteristics.

So far, we have discussed ways of monitoring the production process to ensure that it is in a state of control and that there are no assignable causes of variation. A critical aspect of statistical quality control is evaluating the ability of a production process to meet or exceed preset specifications. This is called process capability. To understand exactly what this means, let's look more closely at the term specification. Product specifications, often called tolerances, are preset ranges of acceptable quality characteristics, such as product dimensions. For a product to be considered acceptable, its characteristics must fall within this preset range. Otherwise, the product is not acceptable. Product specifications, or tolerance limits, are usually established by design engineers or product design specialists.

For example, the specifications for the width of a machine part may be specified as 15 inches ±0.3. This means that the width of the part should be 15 inches, though it is acceptable if it falls within the limits of 14.7 inches and 15.3 inches. Similarly, for Cocoa Fizz, the average ...