• @chebetz I apologize for not getting back to you sooner. I had some IT issues and some other stuff that came up. I am seeing the same thing you are seeing 11 months, 2 weeks ago

  • Hi @chebetz,

    Your readings are correct. Probably the author altered the numbers but didn’t reflect that on the graphs. Happens to all of us once in a blue moon.



      11 months, 2 weeks ago

  • @Chebetz That was my interpretation of your post. What you are seeing is the typical reaction to doing something that doesn’t match what people put in books. I have always had issues with rules to some extent. This is paraphrased but “I didn’t care yesterday. I don’t care today. I won’t care tomorrow.”

    I have always been more concerned with…[Read more]

  • @chebetz I have seen this same issue repeatedly since my first control chart in 1983. I have never had a decent answer and yes I have always heard the sample size of 30.

    This is what I do. I do 25 subgroups of 5 (preferably 5). 1 year, 1 month ago

  • @chebetz I need you to clear something up. In your post you spoke about adding spec limits to the control chart i.e. “What harm could come from including these two additional lines on a control chart (other than the possible confusion a reader could have and mix up the control and specification limit lines)?” My interpretation of that comment is…[Read more]

  • @chebetz, @rbutler and @straydog Just to do one upsmanship I found this site in 2001. I was being sued for violating a noncompete so I couldn’t work for myself. The guy suing me used time as a strategy and dragged these things out trying to run you out of money. It also gave the market time to forget you and move on. I dedicated 4 hours a day to…[Read more]

  • Well @Straydog and @Mike-Carnell that guy @chebetz has found us out!  I guess it’s time we ask Mike Cyger to tell Katie to change our screen names again. I think I’ll go with Dr. Theodore Sabbatini this time around.  :-)

    I can’t answer for Straydog or Mike but given our interactions over the years I’m pretty sure their answer will be the same a…[Read more]

  • @chebetz I am with @rbutler and @straydog on some level. There is no statistical jail. You want them on there put them on. Don’t put them on and walk away. Pay attention to what you have done and make sure you aren’t causing a mess. This whole thing is about continuous improvement. You want to try something, do it and if it works keep doing it and…[Read more]

  • I’ve messaged Minitab technical support to chime in, @chebetz. 1 year, 8 months ago

  • @chebetz 30 is a rule of thumb. Like all rules of thumb it only says something about reasonableness. You’re optimum sample size depends on the size of the population and your desired confidence level. You only need 2 samples for statistical analysis. But that may be far too small to give reasonable confidence. For 100% confidence you need to…[Read more]

  • To add to what @Daniel.S, @KatieBarry, @Mike-Carnell, and @Cseider have said. The posts you have made to this forum present you in the light of someone who expects everyone else to do all of the work for them. Your posts also give the impression that you have neither made any attempt to investigate anything on your own using things like Google…[Read more]