A quality control chart that analyzes a specific attribute of a product is called a univariate chart, while a chart measuring variances in several product attributes is called a multivariate chart.

In many control chart applications, it is useful to relate the variation of the process to other variables that are being observed simultaneously with the variable that is charted. You can use the ...

Independent variables can be charted individually, but if the variables are correlated, a multivariate chart is needed to determine whether the process is in control.

In Part I of this article series, the authors discussed the regression control chart method for identifying out-of-trend data in pharmaceutical stability studies. In Part II, the by-time-point method ...