Chapter 13 Supply Chain

Statistical quality control (SQC)

A number of different techniques designed to evaluate quality from a conformance view. How well are we doing at meeting the specifications that have been set during the design of the parts or services we are providing?

Managing quality performance using SQC techniques usually involves:

• Periodic sampling of a process

• Analysis of these data using statistically derived performance criteria

Assignable variation

Deviation in the output of a process that can be clearly identified and managed

Assignable variation example:

Variation caused by workers not being equally trained or by improper machine adjustment

Common variation

Deviation in the output of a process that is random and inherent in the process itself

As variation is reduced, quality is ____

Improved

Upper and lower specification levels

The range of values in a measure associated with a process that is allowable given the intended use of the product or service

Capability index

Used to measure how well our process is capable of producing relative to the design specifications

Capability index formula

Ratio of the range of values allowed by the design specifications divided by the range of values produced by a process

Process control

Concerned with monitoring quality while the product or service is being produced

Typical objectives of process control plans:

• Provide timely info about whether currently produced items are meeting design specifications

• Detect shifts in the process that signal that future products may not meet specifications

Statistical process control (SPC)

Techniques for testing a random sample of output from a process to determine whether the process is producing items within a prescribed range

Attributes

Quality characteristics that are classified as either conforming or not conforming to specification

Variables

Quality characteristics that are measured in actual weight, volume, inches, centimeters, or other measure

If the mean is exactly in the center and capability index = 2, then 2 defects per ___ are expected

Billion

What is the minimum number of samples suggested for control charts with variable measurement?

25

Where can statistical quality control be applied?

Manufacturing, service processes, logistics

A higher value of Cpk implies a ____ number of defective parts

Lower

Testing a random sample of output from a process to determine whether the process is producing items within a preselected range

Statistical process control

When the product or service can have more than one defect per unit, what is the most appropriate chart?

C-chart