Statistical Quality control is the application of statistical methods to the monitoring and control of a Quality to ensure that it operates at its full potential to produce conforming product. Under SQC, a Quality behaves predictably to produce as much conforming product as possible with the least possible waste. While SQC has been applied most frequently to controlling manufacturing lines, it applies equally well to any Quality with a measurable output. Key tools in SQC are control charts, a focus on continuous improvement and designed experiments.

Much of the power of SQC lies in the ability to examine a Quality and the sources of variation in that Quality using tools that give weight to objective analysis over subjective opinions and that allow the strength of each source to be determined numerically. Variations in the Quality that may affect the quality of the end product or service can be detected and corrected, thus reducing waste as well as the likelihood that problems will be passed on to the customer. With its emphasis on early detection and prevention of problems, SQC has a distinct advantage over other quality methods, such as inspection, that apply resources to detecting and correcting problems after they have occurred.

In addition to reducing waste, SQC can lead to a reduction in the time required to produce the product or service from end to end. This is partially due to a diminished likelihood that the final product will have to be reworked, but it may also result from using SQC data to identify bottlenecks, wait times, and other sources of delays within the Quality.