Ten Things to Know When Using the Individuals Control Charts

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Thanks so much for reading our publication. We hope you find it informative and useful. Happy charting and may the data always support your position.


Dr. Bill McNeese
BPI Consulting, LLC

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Comments (5)

  • Edson R. MontoroMarch 30, 2022 Reply

    Tahnks for your insightful paper, as usual! The transformation data war is really very interesting, Mr. Montgomery approves it and  Mr. Wheeler does not, in my training sessions I discusse this two options with my trainees, and in my humble opinion, when Shewhart created the SPC concept he didn't transformed a nonnormal data to a normal distribution., this is my approach. Best Regards. 

  • Ângela Lopes PintoApril 13, 2022 Reply

    Very nice text!!!

  • H. W. (Hank) Fahrlander Jr.May 10, 2022 Reply

    Control limits for charts of individuals work fine if the distribution of individual values is normally distributed.  Shewart utilized the Central Limit Theroeum as th basis for recommending charts of avrages and ranges as the distribution of averages is normally distributed regardless of the shape of individuals.. This is especially trtue when the number of individual  values used to calculate the average is at least 4 and preferabbly 5 or more.  For example in a chart of averages and ranges, the sample group should be taken close together to reflect the short term variation of the process and the time between sample groups should reflect the time to time variation.Shewerts whole concepts were based on the use of the charts as a tool to tell the operatorv when the process is running in a stable or unstable mode and when to take action when it is unstable (special cause variation).  He never liked using his charts to display process data after the fact which was too late to take action to prevent the process from continuing to make defective product.Hank.

  • Leslie LSeptember 22, 2022 Reply

    What a wonderful resource! Thank you.Can you tell me how to input phase lines in an I-chart to indicate a process change?  I didn't see mention of this in your paper or on this website.

    • billSeptember 24, 2022 Reply

      The easiest way of course is to use our SPC for Excel software.  You simply select where you want to split the control limits and go to the actions panel on sthe SPC for Excel ribbon.  Manually, you calculate each phase separately.  Let me know if you need more information.

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