Projections and the U ² Multivariate Control Chart

AbstractA projection approach to designing multivariate control schemes is used that simplifies the construction and understanding of these charts. The method is applied to construct charts that are sensitive to specific assignable causes such as a mean shift that affects only a subset of the variables and a model-fixed assignable cause that can occur when one variable causes another. The projection results in a chart that is easy to compute and design and it has greater sensitivity than a chi-square chart for the assignable cause under study. Furthermore, the chart can be analyzed using the convenient central and noncentral chi square distributions when the process is on-target and off-target, respectively.KeywordsAverage Run LengthChi-Square Control ChartsMultivariate Control ChartsStatistical Process Control Additional informationNotes on contributorsGeorge C. RungerDr. Runger is an Assistant Professor in the College of Business and Management. He is a Member of ASQC.