iSixSigma

Eileen

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  • Charles,
    Thanks for all your comments on this topic. I have being reading the thread with interest. I decided not to add any more comments because you clearly defined the issues. I have already had this discussion with the individuals involved. You won’t change their perspective – at least not in a couple of months.
    They really need to go back…[Read more]

  • As I said before. You need to read and study the work done by Dr. Shewhart. Since he developed and established the theory of the control chart, I feel he is more qualified on this topic than you. I am sorry, but you are so wrong.
    Eileen

  • Nonsense!! There are no probability values associated with control charts. There are no alpha and beta risks associated with control charts. Control charts are not tests of hypotheses. Read Walter Shewhart’s book – Economic Control of Quality of Manufactured Products and/or Dr. Deming’s “Out of the Crisis”
    Eileen
     

  • Jim,
    Thanks for your postings. I think you asked some really good questions in spite of your lack of sleep.Fundamentally, I think we are in agreement. Although statistics is useful as an aid to make judgements, it is not a substitute for good engineering knowledge. Of course we could use statistical models and make a boat load of assumptions and…[Read more]

  • Jim,
    Again, I think much of this has been abused and the method of statistical analysis has been twisted. The so-called long-term study was intended to study variation as it happened in production. Simple example is a lathe. During production runs you would experience tool variations, more raw material (bar stock) variation as well as maintenance…[Read more]

  • Jim,
     
    I have read your postings on this topic with great interest.
     
    I agree with you that you can conduct a capability study and calculate the Cp and Cpk for that study. Perhaps, I can explain the use of the other notations associated with a capability study.
     
    The use of the different notations were used by Ford Motor Company. Sp…[Read more]

  • RadheshyamThank you for your kind email. Feel free to send me your issues and I will do my best to help.
    I tried to send you an email directly but the email came back saying the server was not found(?).
    My email is [email protected]
    Eileen BeachellQuality Disciplines

  • Radheshyam
    I think you raise a good point. My experience with cutting machines shows that more factors are involved than simply the tool. Although critical to it’s performance, other factors need to be investigated to achieve a high level of Cpk. Those factors will depend on the type of machine you are testing. Once you have selected the most…[Read more]

  • Eileen replied to the topic What is Cpk? in the forum General 19 years, 5 months ago

    Scott,
    You really started my day off with a good laugh. Vic and I worked together for many years. He would enjoy this one! He had nothing to do with defining the k in Cpk. Although his paper on Capability Indices is excellent, the index has been around for many decades. It can be found in some AT & T material from the 50’s and 60’s. I do not know…[Read more]

  • Eileen replied to the topic Reliability Question in the forum General 19 years, 7 months ago

    Scott,
    Good question but not a simple answer. There is a basic test called the mean ratio test. This test simply takes the ratio of the mean life of the test group over the control group.This hypothesis test, along with most of them in reliability, assumes only one known population slope. I am assuming you are using a Weibull distribution[Read more]

  • Eileen replied to the topic Classic DOE video in the forum General 19 years, 7 months ago

    Chad,
    This tape is a classic. It was done at Xerox. I was doing Six Sigma training at Xerox in 1999-2000 and had asked several classes about this tape. No one remember it. Finally, a grizzled engineer (or should I say seasoned) discussed the tape with me. It is no longer available from the company. They made me a copy of the tape and you may find…[Read more]

  • Eileen replied to the topic FMEA, controls in the forum General 19 years, 8 months ago

    Jon,
    It depends on what you have in the columns for severity and frequency of occurrence. The decision to take action is frequently tied to the RPN number. The higher the number, the more likely you should do something. If you have ones in severity and occurrence, then you probably don’t need to take any action. However, if it is a safety…[Read more]

  • Ron,
    Yikes! I wonder what Don Wheeler was thinking?
    The measures for skewness(asymetric) and kurtosis(peakness or slope of the sides of the distribution) are used extensively where process capabilities are determined. The most common method for determining the best model (or distribution) for your data is the four moments test (or versions…[Read more]

  • Zilgo,
    I really don’t agree with you. First of all, why do you think Jon is comparing means? It is more likely with a measurement system there is one single value. There are exceptions to this but I would guess this his situation. So how do you use a test of means to compare one individual value to the avg. of 3? This is clearly an abuse of…[Read more]

  • Anon,
    Nope. Neither can you do any type of statistical analysis – including a t-test. Let me give my assumptions:
    This is a standard that is being measured or at least a golden part.
    There has already been a gage R & R conducted prior to actually using the gage
    AND there is already a record of measures on the standard which could be the basis…[Read more]

  • Jon,
    Forget the t-test. Not appropriate. I had a discussion with Dr. Deming on this very issue. He was very adament that the most useful and appropriate method for the analysis is a statistical control chart. If the value 7 is outside the control limits, then you need to take action. Somthing has in fact changed. If the 7 is within the control…[Read more]

  • Eileen replied to the topic Machine capability in the forum General 19 years, 9 months ago

    Most of the initial assessments for machine capability were started in automotive. There were general guidelines established for purchasing of new equipment. I think you need to think about the type of equipment you are purchasing and the appropriateness of the specifications. Consider this in terms of economics, competitiveness, and what the…[Read more]

  • Eileen replied to the topic Mid points in DOE in the forum General 19 years, 9 months ago

    No problem. In the most common DOE designs (where each factor has two levels), the response is assumed to be linear. A line is drawn between the low level effect and the high level effect for each factor and interaction. Sometimes, there is a question about whether the response may be non-linear (exponential, for example). If there is any doubt,…[Read more]

  • Khaljd This is an easy one. Yes you can use the standard gage r & r. The challenge is to find an alloy or material that is homogenous. You need to take paired samples (cut your dog bones next to each other). The first will be used as the first “measurement” and the second will be the second “measurement”. I have done this numerous times and have…[Read more]

  • Eileen replied to the topic Flowmeter gage study in the forum General 20 years ago

    Cindy,
    I urge you to conduct a gage R & R on your flowmeters. They can be from a very good company and still have issues. I have consulted with companies and always insist on a precision (gage R & R) study on the flowmeters. They are very critical to performance and need to be viewed from that perspective.The study is most easily done off-line.…[Read more]

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