Mathematics of Control Charts
Digital control charts use logic based rules that determine "derived values" which signal the need for correction. For example,
- derived value = last value + average absolute difference between the last N numbers.
Most SPC charts work best using numeric data with Gaussian assumptions. Recently a new type of control chart, the real-time contrasts chart was developed in order to handle process data with complex characteristics. Such data might include high-dimensional data; mixed numerical and categorical data; data with missing values; and data with non-Gaussian distributions or with non-linear relationships.
Read more about this topic: Statistical Process Control
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