Just more information: There is a section in INTRODUCTION TO STATISTICAL QUALITY CONTROL, Douglas C. Montgomery, 2nd edition, John Wiley and Sons, New York, 1991, Pg 259 example 6-11. It is called misapplication of Xbar and R charts. Says they were trying to use fraction nonconforming on xbar and r chart format (five samples of percentages) to get more information from the data. Montgomery goes on to state that it is incorrect because an inspection processes produces attribute data governed by the binomial distribution. He goes on to plot both. While in his plots, he doesn't see the harm in using the Xbar and R, he doesn't see the added benefit. There doesn't seem to be anything about the Individuals and moving range usage - ---------- From: Dave Willhard[SMTP:[log in to unmask]] Sent: Thursday, March 27, 1997 5:42 PM To: [log in to unmask] Subject: SPC chart for % defective Dr. Donald Wheeler in several of his "SPC Toolkit" columns in Quality Digest has seemed to suggest that Individual X / Moving Range control charts can be used to control attribute data such as percentage defective, first pass yield, etc. Most SPC textbooks only list standard attribute charts (P, C, etc.) when discussing that type of data. Does anyone currently use a "variables" type chart to control attribute data? I would like to use an X/MR chart rather than a P chart for % defective because it's easier for operators to plot. I'm just wondering if it's really valid. Dr. Wheeler gives examples of X/MR charts used for this type of data but never really explains the concept of why it is valid to use them rather than standard attribute charts. Dave Hall Quality Engineer Compeq International <[log in to unmask]> *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************