Statistical Process Controls (SPC) is a suite of methods that can be employed to control a manufacturing or assembly process. It has a wide range of potential applications ranging from consumer products to defense. It can be employed at the lowest element of component manufacturing or an assembly operation.
This article discusses the assumptions necessary to understand SPC.
- The process is stable and in control.
- The data are independent of each other.
- The data of each subgroup are identically distributed.
- Real valued data are approximately normally distributed and counting data may be approximated by the normal distribution.
- A measurement can occur in only one subgroup, i.e., sampling without replacement.