ASQ

Exclusive Content & Downloads from ASQ

On Properties of Q Charts for Variables

Summary: The sensitivity of four tests on Shewhart type Q charts and of specially designed EWMA and CUSUM Q charts to detect one-step permanent shifts of either a normal mean or standard deviation has been studied. The usual test that signals for one point beyond three standard deviations on a Shewhart chart is found to have poor sensitivity, generally. The test that signals when four out of five consecutive points are beyond one standard deviation in the same direction is found to be a good omnibus test. The EWMA and CUSUM Q charts are the most sensitive and are about comparable in overall performance.

Anyone with a subscription, including Site and Enterprise members, can access this article.


Other Ways to Access content:

Join ASQ

Join ASQ as a Full member. Enjoy all the ASQ member benefits including access to many online articles.

Subscribe to Journal of Quality Technology

Access this and ALL OTHER Journal of Quality Technology online articles. You'll also receive the print version by mail.

  • Topics:
  • Keywords: Control charts,Q chart (quality score),Variation
  • Author: Quesenberry, Charles P.
  • Journal: Journal of Quality Technology