Ken Feldman


  • Check out something referred to as the 1.5 sigma shift. There has been much debate on this site as to the source and validity of the concept. It will explain why the traditional 3.4 defects per million definition of 6 sigma shows up in the Z table as 4.5 sigma and not 6. 4 months, 1 week ago

  • As an analogy….once you reach your desired weight after a diet, do you stop weighing yourself? No. You keep monitoring your weight to be sure it doesn’t change. The same would be true if you reach your desired blood pressure because you are taking drugs to help you. You would still periodically take your blood pressure to make sure nothing…[Read more]

  • @rbutler Robert, as usual, a concise simple to understand explanation LOL. I always learn so much from your posts…at least the parts that I understand. Hope all is well. 1 year, 5 months ago

  • @shar6580 Double check the correctness of your assumptions. The only assumption for normality is in the residuals. There is no normality assumption for the raw data. Save your efforts of all those transformations. 1 year, 5 months ago

  • @rbutler  Glad it isn’t just me.  People must be so bored that they are getting back onto (LOL) and so desperate for something to do they are responding to decade old posts.  Next might be responses to test questions or dissertation topics from people who graduated a decade ago.  We might even see someone pop in to comment on the…[Read more]

  • Then you can see above that the power for your data is only 38% which means if there is a difference you only have a 38% chance of seeing it.  With a sample size of only 10, there will be a significant overlap of the two confidence intervals so it will not be easy to see a difference.  I would not make a decision that the two groups are s…[Read more]

  • P-value for normality for Sample 1 is .485 and for Sample 2 is .020.  Close enough with respect to the normality assumption.  In that case, maybe the 2 sample t can be used.  The p values for the equal variances are just a bit above .05 so maybe close enough.  Bottom line is that maybe the 2 sample will work in this case.  Since no difference was…[Read more]

  • Not sure I understand what values you put into Minitab for difference in means.

    I think I found that 10+10 items should give at least 90% power for the differences to be assessed 2 years, 6 months ago

  • @fausto.galetto  Since you were not able to reject the null hypothesis and see a difference, I would want to know the Power of your tests.  Given the small sample sizes is there no difference as you state or is the lack of noticeable difference due to a low power? 2 years, 6 months ago

  • Hey Katie,

    Maybe time to close this thread.  This Fausto guy is really a whack job.  He will not be convinced so maybe Chris, Robert and David can stop humoring him and he will go away.  Hope all is well with you and Fake Mike. 2 years, 8 months ago

  • WOW!!!!!!  This thread is soooo coooool.  Reminds me of the good ole days when the argument was about the 1.5 sigma shift.  Only thing missing from this thread is Stan challenging Fausto to a duel and debate.  @rbutler  This is the most I have seen you write and argue in the many many years I have followed your posts.  Its been a blast.  I know t…[Read more]

  • Process appears to be in control.  Both Weibull and Exponential seem to be good fits for the data.

    T Chart of C1


      2 years, 8 months ago

  • @rbutler, @fausto.galetto


    The Montgomery example appears to be from one of his books published in 1996.  He uses the I/MR chart with transformed data to create a control chart of MTBF which is obviously going to not be a normal distribution.  Since that time, Minitab has brought out the G and T charts for time between rare events.  Po…[Read more]

  • Haven’t seen a lot of that in the industry.  Some folks talk about it but I have not seen anyone actually execute it.  On the other hand, I have seen GBs have a requirement for re-certification by having to do another project.  Since MBBs and BBs are usually full time, their skills usually don’t deteriorate.  There is opportunity for constant eva…[Read more]

  • @katiebarry, @mike-carnell, @cseider, @rbutler.

    You guys are so lame!!!!  CCPS is Center for Chemical Process Safety.  This is not to be confused with EPSC or European Process Safety Center.  We are having a joint conference Oct 1-2 in Frankfurt, Germany.  The recommended hotel is the Maritim Hotel Frankfurt.  Coincidentally, I have stayed ther…[Read more]

  • @KatieBarry, @mike-carnell

    Jeez…, restaurants, Uber….what kind of woosie run is FM doing???  How about sleeping out under the beautiful Fall sky with the sparkling stars….hunting and gathering his food and fishing from the running rivers and drinking water from the mountain fed lakes.  That’s what Real Mike would do if he didn’t h…[Read more]

  • @mike-carnell   It is nice that you remember old Darth.  It’s just that I can’t recall you ever being nice to me.  You, Robert and Chris sure are active again posting sometimes useful information.  Has anyone spoken to Fake Mike to see if he is interested in revitalizing the Forum or getting back into the Conference business?  Even the Brady Bunch…[Read more]

  • @bayankamal

    Let’s make sure that you are truly understanding what you are doing…..  The null hypothesis would be that the population mean that Sample A came from is the same as the population mean that Sample B came from.  You are NOT testing whether the means of the two samples are different.  The alternate hypothesis can be that the po…[Read more]

  • The definition of “null” is having or associated with the value zero.  Therefore all null hypotheses will be in some form indicating an absence of something.  In the two sample t test for example, the null is that the difference in the population means of the two samples is zero or no difference.  In regression, the null hypothesis is that th…[Read more]

  • @mike-carnell   Ahhh, yes the classic response to update your resume and run away.  Still valid decades later.  Lest we also not forget the act of chair throwing to those who are most inept in their questions.  Our deployment at DPS was going great under the leadership of the CFO and CEO.  But once they were sold and the CFO and CEO left the need…[Read more]

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