Introduction to SPC (Statistical Process Control)

Manufacturing involves an attempt to produce items that as closely as possible meet design specifications (e.g., size, strength, etc.). However, all production processes exhibit variation --- that is, no two items are identical. What method can be used to reduce such variation? The classic and still most widely used method is called SPC or "statistical process control".

All companies want to improve the quality of their products. Attempts to improve product quality need to be structured in such a way that they have a reasonable chance of success and the cost/benefit ratio is appropriate. The most successful method available for such endeavors is called SPC (statistical process control). SPC can also be used to meet ISO requirements for "continual improvement" as well as FDA requirements to "control and monitor production processes". SPC can even be used to monitor complaint rates, to determine if there has been a "significant" increase in complaints, which would therefore trigger an MDD "vigilance report" and/or an FDA MDR submission.

SPC is a statistical tool that objectively identifies when it is worthwhile to perform a formal investigation of manufacturing variation, in order to identify and mitigate its cause. SPC continually adjusts its sensitivity in order to ensure that such investigations are performed only when there is a reasonable chance of identifying causes of variation. SPC also provides information that can be used to estimate what % of items is being produced "in specification".