On the Performance of Sequential Procedures for Detecting a Change, and Information Quality (InfoQ)

The concept of information quality (InfoQ) is defined as the potential of a dataset to achieve a specific (scientific or practical) goal using a given empirical analysis method. InfoQ is derived from the utility (U) of applying an analysis (f) to a data set (X) for a given purpose (g). Formally, the concept of Information Quality (InfoQ) is defined as: InfoQ(f, X, g) = U(f(X | g)). The literature on statistical process control has focused on the Average Run Length (ARL) to an alarm, as a performance criterion of sequential schemes. When the process is in control, ARL0 denotes the ARL to false alarm and represents the in-control operating characteristic of the procedure. The average run length from the occurrence of a change to its detection, typically denoted by ARL1, represents the out-of-control operating characteristic. These indices however do not tell the whole story. We suggest the use of probability of false alarm (PFA) and conditional expected delay (CED) as an alternative which enhances the information quality (InfoQ) of statistical process control methods. As an extension, we discuss the concept of a system for statistical process control in the context of a life cycle view of statistics (http://spclive365.com).