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Have i reached 6-sigma?

Six Sigma – iSixSigma Forums Old Forums General Have i reached 6-sigma?

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  • #42326

    rugB
    Member

    A basic question: how & when do i know that my process has achieved 6-sigma without doubt?
     i mean, Is there any way or indication that i can measure & get  the feedback from my control chart of the process to know whether it is nearing 6-sigma or it has already achieved it & be 100% sure of it? 

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    #133587

    wrong
    Member

    From the nature of your question, you will probably never know, you have learn first.

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    #133590

    Ken Feldman
    Participant

    You can be 100% sure that your process is functioning at a 6 sigma level when all the points on your control chart are within 1 s.d. of the center line.  At least that is what my mentor, Stan, has taught me.

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    #133593

    Mr IAM
    Participant

    What? I really hope your just joking.  Right?
    Otherwise, Wrong is Right.

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    #133595

    Ken Feldman
    Participant

    Check previous threads and you will see that would be one of the more benign names Stan has been called.  The fun is always in seeing what kind of responses come out when something really dumb is posted, both the question and the answer.

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    #133596

    Mr IAM
    Participant

    I would suggest searching for some information on “capability analysis” or “measuring process sigma”.
    Control charts do not have Specifications on them.  You need to compare your process data to the specifications, not the control limits to determine your process capability.
    Do you know what your Cpk or Ppk are?

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    #133597

    Ken Feldman
    Participant

    Thought it was an appropriate response for the nature of the question.  Plus you know I never ever kid around or use humor in this Forum :-).  Thanks for giving me the benefit of the doubt.

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    #133598

    Ken Feldman
    Participant

    I liked my answer better. 

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    #133600

    Mr IAM
    Participant

    Yeah… if it was some numbskull doing a “test” I’d agree with your approach.  :-)

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    #133609

    BTDT
    Participant

    Rug8:

    Rug8:As others have pointing out, process capability does not
    come from a control chart using Upper and Lower Control Limits (UCL and LCL),
    but comes from a calculation of process capability using Upper and Lower Specification
    Limits (LSL and USL).You can calculate a confidence interval for any parameter
    you care to pick. The difficult part is to determine the distribution of the
    sampling error. You will have a t-distribution for the mean, and a Chi-square
    distribution for the standard deviation used in the calculation of Z. I have
    not seen a formula and determining the distribution from first principles is
    beyond me.I used bootstrapping to calculate a 95% confidence interval
    for a Z value once, because the MBB did not believe the rather large value of Z
    from the BB when using as few as 13 randomly selected data points. The
    confidence interval ended up being non-symmetric about the mean and was about
    7.3-11.3.The MBB was satisfied that the application was capable enough
    and was at least 6 Sigma.The project was to design and implement a new change
    detection and sampling algorithm for a remote, real time control system. The
    idea was to decrease the sampling and data transmission costs while maintaining
    adequate control.Cheers, BTDT

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    #133628

    Dog Sxxt
    Participant

    Just accept whatever a company says in the newspapers that they are a 6-sigma company.
    If people still do not understand the basic stuff like what is control limit and what is spec limit, t’s better to re-open SPC textbook.

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    #133677

    rugB
    Member

    Thanks for the insight people,
    here’s the situation,
     we’r using a p-chart in the shop floor for a process which has a mean of 9% (defective)presently, we want to move towards 6sigma or zero defects, So how do we set our targets in terms of sigma? Is there any other feedback tool simple enough for the operators in the shopfloor to understand what we’r striving for?
     
     
       

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    #133683

    Get a Life
    Participant

    Darth and Iam:
    You guys have pretty much ruined this site.  I know neither one of you have a life, but calling everyone that doesn’t know as “much” as you about Six Sigma stupid is very small-minded of you.  I know a lot of extremely smart people who haven’t been exposed to 6s and are willing to change their mindset, but if they come to this site, you guys make it look like a dork-a-thon.  You should go to a good Star Trek convention and leave this site alone.  By the way, what do either of you do for a living?  I guarantee it isn’t even close to management….

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    #133686

    Ken Feldman
    Participant

    Dear Get a Life,
    It always amuses me when a poster tells me to get a life when he/she apparently spends sufficient time lurking to have a history of my posts.  The difference is that I along with many others do try to contribute when appropriate rather than just lurk and take cheap shots. 
    To answer your other question, I am a retired military commander who “managed” hundreds of thousands of men/women in battle if that counts as “management”.  I am now homebound and disabled due to injuries sustained in a major battle on a volcanic planet.  Many of my injuries have required replacement using bionic parts.  As a result I can’t have a normal life plus my two children from the wife I killed have turned on me.  Finally, Star Trek is for weanies and dorks and I wouldn’t be caught dead or alive at one of those conventions.  Since I currently live in Denmark, I will allow you the freedom to post your comments rather than make you feel the darkside of the Force.

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    #133695

    Darth’s Mother
    Participant

    Disagree

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    #133706

    Dr Sigma
    Participant

    The best way to tell is the simplest way — less than 3.4 defects PMO.  Without a million opportunities (which isn’t very many in most companies/processes because each finished part usually has hundreds of opportunities throughout the supply chain), you should determine if your sample is representative of the population using t and z tests.

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    #133720

    Mr IAM
    Participant

    Hmm.. Interesting. 
    1) I have never claimed to know everything about six sigma.  I participate on the site because I continue to learn from those that post here – specifically Darth, Carnell, BTDT etc…
    2) I have never called anyone stupid.  Can you point to a post where I have done that?  Good luck finding one.  Those of us that participate in the forum a lot get frustrated by those who are; a)posting test questions b)ask basic questions that they could find in 1 click elsewhere on the site c)respond to posts that are 4 years old.  Still, I have never called anyone stupid.
    3) If you look at 99%+ of my posts you will see I am responding sincerly to a question.
    Cheers!

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