iSixSigma

TomF

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  • TomF replied to the topic DPU Vs DPMO in the forum General 18 years ago

    Mike,
    I had challenged you to give me a constructive counter-arguement to my interpretation of Deming’s quotes.  You have responded with an insult.  My challenge for you to reply with something constructive still stands. 
    By the way, the issue is not whether DPU and DPMO are performance type metrics.
    Tom

  • TomF replied to the topic DPU Vs DPMO in the forum General 18 years ago

    Mike,
    First, I must say that I do not appreciate the demeaning manner in which you reply to others’ posts.  I would hope that people using this site would respect each others opinions and offer constructive comments.
    If you disagree with my interpretation of the Deming quotes, please let me know why you disagree with them.  Summarily d…[Read more]

  • TomF replied to the topic DPU Vs DPMO in the forum General 18 years ago

    This may come as a shock to you but just because CEO’s compare apples to oranges that does not make it a valid use of metrics.
    Indeed, W. Edwards Deming talks about this misuse of metrics in two of his seven deadly diseases. 
    Evaluation of performance, merit rating, and annul review.  To quote Mary Walton’s excellent book “The Deming M…[Read more]

  • TomF replied to the topic DPU Vs DPMO in the forum General 18 years ago

    Mike,This may come as a shock to you but there is as much of a relationship between free throws, passing, hitting and athleticism as there is a relationship between light bulbs and jet engines.  Namely, professional sport teams may share the same name.  The plants making the light bulbs and jet engines share the same name.Tom

  • TomF replied to the topic DPU Vs DPMO in the forum General 18 years ago

    Let me clarify a few things by putting the concepts in bullets:
     

    There is a famous quote by George Box:  “No model is right, some are useful.”  There are disadvantages in using both DPMO and DPU.  You need to be smart in choosing which one to use.  Consider which of these metrics will help you make the greater amount of economic gain.…[Read more]

  • TomF replied to the topic DPU Vs DPMO in the forum General 18 years ago

    You are talking about comparing apples to oranges (or light bulbs to jet engines). 
    Consider that a typical NBA players makes between 90% to 70% of their free throws.  A NFL quarterback completes between 70% to 40% of their passes.  And the best major league baseball players gets a hit approaching about 40% of the time.
    By these numbers, we can…[Read more]

  • TomF replied to the topic DPU Vs DPMO in the forum General 18 years ago

    AbetF–I am confused.  Perhaps because it is late here. 
    AbetF says “( in mike’s example of resistor = best soldering result ). But you cannot achieve this ” best soldering result” if you don’t list all possible failure modes and do your best to avoid these failure modes or “opportunities for defects .”  However, I read Mike’s example as co…[Read more]

  • TomF replied to the topic DPU Vs DPMO in the forum General 18 years ago

    I am not sure why Stan does not agree with Ron.  In my opinion, it is more important to drive improvement than to go “by the book” on counting opportunities.  Use what makes the most economic sense.
    Stan–can you elaborate more on why you disagree.
    I have worked for a company that have tried to count EVERY opportunity.  I felt like they were sp…[Read more]

  • Hi Jim,
    Thanks for your input. 
    You are right about Poke Yoke addressing the root cause in your example.   I guess I was thinking of Poke Yoke as functional gaging only and did not consider fixturing.  My mistake.
    I am a little confused by your corrective action definition because you have the word “prevent” in the corrective action def…[Read more]

  • I looked up this topic because I was hoping somebody had an short definition I could paraphrase in a report.  Since there isn’t anything posted that fits this bill, I will give you my definitions and would be glad to hear feedback to hone this solution to an accurate, short definition.

    Disposition: The decision what to do with discrepant hardwa…[Read more]

  • Hi Steve,
    Good question.  Since we want to separate common cause variation from natural variation, I would recommend not transform the data by including any bonus tolerancing in your control chart data.
    If you took the control limits of one axis (call it the X axis) and the control limits of the other axis and plot these perpendicular to each…[Read more]

  • TomF replied to the topic DOE Sample Size in the forum General 19 years, 5 months ago

    Hi Marty,
    I apologize if I didn’t express myself clearly. 
    I believe that in most typical fractional factorial DOE’s replication does not add value to the experimental results.  This is because the ANOVA already calculates and compares averages. 
    It sounds like you have done your homework.  I hope your experiment is successful.
    Tom F

  • TomF replied to the topic DOE Sample Size in the forum General 19 years, 5 months ago

    Hi Marty,
    The philosophy regarding DOE’s that I, personally, have bought into is:  Get the information you need at minimal cost.  Remember that DOE’s are expensive.  You want to get results–even if it is that there are no significant factors. 
    This philosophy would suggest that you use one trial and not replicate each trial.  Otherwise, you c…[Read more]

  • Hi Kenny,
    From my understanding of your question, it appears as though you are “putting the cart before the horse.”  It seems to me that you are using statistical principles to develop a somewhat arbitary limit to compare a sample to initiate a change.  Control limits should be set based upon past history, not a goal.
    As previous posts have men…[Read more]

  • TomF replied to the topic OC Curve and Sampling Plan in the forum General 20 years ago

    Hi Thom,
    I wanted to explicitly state the results of your Texas Lotto example and clarify your point to prevent anybody from misunderstanding your posting.
    Using the binomial distribution, the probability is approximately 0.000188% while using the hypergeometric distribution is approximately 0.000004%
    Don’t be misled that the binomial…[Read more]

  • TomF replied to the topic Rolled Throughput Sigma / Yield in the forum General 20 years ago

    Hi,
    Suppose that you had a process consisting of three steps.  The yield of the first step is 90%.  The yield of the second step is 80%.  The yield of the third step is 75%.  The Rolled Throughput Yield is 54% (calculated by multiplying .9 , .8 and .75).
    Now suppose that you had 100 parts to start.  90 parts go on to the next step.  10 are defec…[Read more]

  • TomF replied to the topic OC Curve and Sampling Plan in the forum General 20 years ago

    Hi Woey,
    I just stumbled across your posting.  I hope that its not too late to give you help.  The equation for an operating characteristic curve is based on a distribution called the HyperGeometric Distribution
    In constructing a chart, the horizontal axis is based upon the actual percent of non-conforming product in the lot.  The ver…[Read more]

  • TomF replied to the topic Binomial Process Capability Indices in the forum General 20 years ago

    Hi Bob,
    I have read thru this message thread and am disturbed by the responses.  Let me play “devil’s advocate” and point out some of my concerns. 
    It seems to me that calculating a Cpk for a binomial distribution is creating something completely unnecessary.  Other than adding in confidence limits, doesn’t p-bar (the binomial average) tell…[Read more]

  • TomF replied to the topic Variance in the forum General 20 years, 2 months ago

    I hate to contradict anybody, but I need to correct some of the prior statements. 
    Standard Deviation is the square root of Variance–not the other way around.
    It is essentially the average of the deviation from the averages squared.
    Variance = (Sum (Xi – X bar)2)/ n -1
    Standard Deviation = Sqrt ((Sum (Xi – X bar)2)/ n -1)
    Capability can be…[Read more]

  • Thanks Gary,
    I will take your advice and read this book.

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