The double sampling and the EWMA charts based on the sample variances

  • Machado M
  • Costa A
  • 20


    Mendeley users who have this article in their library.
  • 27


    Citations of this article.


We propose a new statistic to control the covariance matrix of bivariate processes. This new statistic is based on the sample variances of the two quality characteristics, in short VMAX statistic. The points plotted on the chart correspond to the maximum of the values of these two variances. The reasons to consider the VMAX statistic instead of the generalized variance {divides}S{divides} is its faster detection of process changes and its better diagnostic feature; that is, with the VMAX statistic it is easier to identify the out-of-control variable. We study the double sampling (DS) and the exponentially weighted moving average (EWMA) charts based on the VMAX statistic. © 2008 Elsevier B.V. All rights reserved.

Author-supplied keywords

  • Control charts
  • Covariance matrix
  • Double sampling
  • EWMA
  • Generalized variance

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document


Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free