A modified median chart with estimated control limits is proposed for monitoring the mean value of a normal process. The estimates for the nominal process parameters used to set up the control limits in Phase I are the average of the sample medians and the average of the sample ranges of m...

In the last few years, multivariate quality control has been thoroughly studied. The control of the population means vector is usually obtained by using multivariate control charts developed for this purpose. Nevertheless, when the goal is the efficient control of the covariance matrix, few...

In the last few years, multivariate quality control has been thoroughly studied. The control of the population means vector is usually obtained by using multivariate control charts developed for this purpose. Nevertheless, when the goal is the efficient control of the covariance matrix, few...