Understanding Statistical Process Control

Statistical quality control (SQC) helps track and improve product or service quality. Statistical process control (SPC) is the primary tool of SQC and encompasses the collection, arrangement, and interpretation of process variables associated with a product, in regard to uniformity of quality.

Every process is subject to variation and therefore there is always room to improve process consistency and quality. To respond to this, adopt a continuous improvement strategy. By repeating the following cycle, a strategy of prevention can be implemented. This is the key to using SPC effectively. Consider the following steps:

• Analyze the process
• What do we know about the variability of this process?
• Is this process statistically controllable (predictable)?
• Is the process capable of meeting the set requirements?
• What considerations are most important to meeting process quality criteria?
• Maintain (control) the process
• Improve the process

SPC encompasses the concepts of variation, statistical control, and process capability, and typically uses the tools XRS control chart, capability chart, and the Pareto chart.

See Also