iSixSigma

six sigma

This topic contains 40 replies, has 14 voices, and was last updated by  sumant 11 years, 11 months ago.

Viewing 41 posts - 1 through 41 (of 41 total)
  • Author
    Posts
  • #48341

    GKP
    Participant

    Sigma being standard deviation ,the less it is , better the control .If it’s correct, why six sigma is better than one sigma .Please answer not with confusion but with simple mathematics

    0
    #162687

    crazy guy
    Participant

    Dont compare six sigma and one sigma in silo. Six sigma is better than one sigma is because you are able to fit in six std deviations within the specification limits, if you have only 1 sigma within the specification limits then 32% of the output would be defects.

    0
    #162690

    GKP
    Participant

    As I told , don’t please try to confuse ,unless you know the subject .With due regards to you ,question remains unanswered

    0
    #162693

    fake accrington alert
    Participant

    Good Question

    0
    #162694

    fake accrington alert
    Participant

    good  answer

    0
    #162697

    GKP
    Participant

    whose answer is good ?

    0
    #162698

    fake accrington alert
    Participant

    Crazy Guy

    0
    #162702

    GKP
    Participant

    But what’s the answer ?

    0
    #162706

    fake accrington alert
    Participant

    Because SS is  equal  to 3.4 ppm and
    One Sigma is  equal  to 697,672 ppm.Is  it  clear  now?
    For  example  the  average  American  company is  at  four  sigma  level ,which is  equivalent  of  0.6 % defective or  6,210 defects  per  million opportunities.
    Sigma  is  a  statistical term that  refers to  the  standard  deviation of  a  process about  it’s mean.In  a  normally distributed  process,99.73% of  measurements will  fall  within +/- 3.0 sigma  and  99.00066% will  fall within  +/- 4.5 sigma.In  a  stale  attribute distributed  process,99.73% of  defective  units,or  defects,will  fall  within probability of  0.00135 and 0.99865.
    Now  if  you don’t  understand  all  that,forget  the SS and  sleep  well.
    best  regards 

    0
    #162708

    Brandon
    Participant

    GKP – you need to do a little more studying on your own before you ask us to give a simple answer to a complex issue.
    Do your own research and if something you find in that effort is still confusing come back here and pose a question.

    0
    #162744

    GKP
    Participant

    It happens to all the big bosses .When they are not knowing the answers ,they will look at his subordinate with either astonishing or humorous look ,as if ,he is telling ” Fellow ,you don’t know the answer of this simple question !!!!!!!!” And tells like you

    “Now  if  you don’t  understand  all  that,forget  the SS and  sleep  well.”
    Sir ,you are not talking to a subordinate and your answer is read by the forum .I would expect a little bit of decorum ,when you answer a question .No , sir , you are not even close to answer. At least ,it’s my views .The question remains open.
    Regards

    0
    #162746

    crazy guy
    Participant

    GKP – Brandon and FAA are big bosses indeed- They have proved their mettle in their own world to their customers and they are here to help without taking money. If they spend the time they spend here working for customers they would be millionaries- so what they do is charity..
    What brandon and FAA are trying to say is please go through your statistics books first before posting your question because the question could look simple but explanation is something which cant be said in a word or two. Since this deals with probability theories its important to understand them before understanding six sigma and one sigma.
    Say for example you have a mean of 50 and LSL of 45 and USL of 60. If your process is at 1 Sigma it means only 68% of the output are within 45 and 60 and rest are outside these limits(how many ever units/oppurtunities you have) and if your process is at 6 sigma it means the 99.99996% of the outputs are within 45 and 60(how many ever units/oppurtunities you have) which means deviations perse should be less such that you are abl to fit in 6 standard deviations within the spec limits.
    Let me try to be more clearer. For a given set of data you find that:
    Mean – 50
    St dev- 2
    If you are able to fit in 6*2 ( which means 99.99996% of the data)falls within your spec limits then your process is at 6 sigma but if you fit only 1*2 then your process is at 1 sigma.
    If if still unclear let me back off…let me not confuse instead of creating clarity…
    Sometimes i wonder whether i need to get back to my basics…
    Regards,
    crazy guy

    0
    #162747

    GKP
    Participant

    Dear Sir ,
    Thanks for your kind response .I would request you not to back off because myself is also going to basics to answer this unique but simple question ,received from my peers . I am sure to get the concept clarified by the esteemed persons of this forum but honestly ,the answer is yet to hit the bull’s eye .Till I’m myself convinced ,I can’t convince others ,with my bullshit jargons.
    Warm regards

    0
    #162748

    fake accrington alert
    Participant

    Crazy Guy
    Very  well  said

    0
    #162750

    crazy guy aka six sigma guy
    Participant

    thanks – FAA..
    wondering how else to make it more clearer. Am i missing here something?maybe nobody asked this question to me ever :)
    In practice, one often assumes that the data are from an approximately normally distributed population. This is frequently justified by the classical central limit theorem, which says that sums of many independent, identically-distributed random variables tend towards the normal distribution as a limit. If that assumption is justified, then about 68 % of the values are within 1 standard deviation of the mean to the spec limits and if your process is so then your process is at 1 sigma and so on and so forth.This is called as empirical rule and I dont question rules( maybe i need to). Maybe we can just leave it at that…
    Regards,
    Crazy guy aka six sigma guy

    0
    #162751

    Six Sigma guy
    Member

    There are two types of Six Sigma followers/experts or whatever u call.. One who take all decisions based on statistics and who know in depth of statistics and secondly those who dont rely much on statistics but use them to validate their assumptions and dont really get into the calculations( which anyways are being done by softwares). I think i belong to the second category of flock :)
    I know how to use softwares,how to make interpretations,how to validate my assumptions and more importantly have business sense.So i dont care much about the formulas of the world and derivations of the world which i leave it to the statisticians and I am not one :) – Should i feel bad about this?

    0
    #162752

    Vidyadhar
    Member

    GKP…
    I can undersatnd ur dilemma… Lets look at a simple example…
    U r manufacturing globes of diameter 100m.. and your customer will only accept only if they are between 98mm to 102 mm..
    98 & 102 are ur specification limits.
    now after you have manufactured a million globes… they might have some variation in diameters.. say ur average dia is 100mm and ur std deviation is at 0.33mm, you can fit 6 std deviations from 100 to 102 and 6 std deviations from 98 to 100. so u will be actually operating on 6 sigma
    on the other hand if ur average dia remains the same and ur std deviation is 1 mm.. U can fit only 2 std deviations between the spec limits to the central value(average).. so u will be operating at 2 sigma level…
    I hope this answers ur question…
     

    0
    #162753

    GKP
    Participant

    Now I am really feeling embarassed to tell that concept of 6 sigma ,is yet see the bright light of the day .But I am sure someone will really clear the concept, in near future, otherwise I will withdraw my question. Anyway ,thanks for your explanation.
    Regards

    0
    #162754

    Vidyadhar
    Member

    GKP….
    If you have any doubts… please post the same…. If you could just rephrase ur question instead using idioms and phrases… I think we could answer ur question….

    0
    #162755

    GKP
    Participant

    May be we are missing the basics .I answered all the inputs, from all of you ,I received , but  my peers are giving me a blank look .I also know that I’m not really convinced myself ,with these answers .I keep the question open.
    Regards

    0
    #162756

    GKP
    Participant

    It’s the effectiveness that counts. If you are excelling in your deliverables ,who bothers , it’s in which sigma ,you are operating .As Ford tells ,we are not here to make cars ,we are here to make money. And this is the ultimate today with fierce competition ,worldover.
    Anyway , I will be waiting for clearing the concept on six sigma ,as I can’t satisfy my peers who feels I am confusing them with all these answers received from my friends.
    Regards

    0
    #162757

    GKP
    Participant

    If it’s linked to my message , I am wondering which idiom or phrases ,I have used ! If not linked , I apolizise .My question is open and it’s very simple question .If you can answer straight ,I will be oblized.
    Regards

    0
    #162760

    sumant
    Member

    Hi GKP,
    your question – “Sigma being standard deviation ,the less it is , better the control .If it’s correct, why six sigma  is better than one sigma”?
    I have made two Sigma’s in 2 different fonts.
    Sigma as standard deviation is not same as Sigma in SIX SIGMA (Here Sigma is known as Sigma Levels), where as sigma as SD known as sigma value.
    Both sigma Value and sigma Level are inversely propotional. When Sigma value is high, sigma level is low and viceversa.
    So when you are saying six sigma, it means your process is operating at six sigma level which is better than one sigma level.
    When Sigma level is higher, process is better, but when sigma value is lower process performance is better.
    Hope I clarified your question.

    0
    #162770

    Brandon
    Participant

    The use of SS to improve business processes cannot be explained solely when one grasps the difference between one sigma and 4 or 5 or 6 sigma.
    GKP – you are either toying with us or nowhere near ready to discuss SS with your superiors. Buy some books and grasp the entire concept before posing any more questions.
    Other posters – I think we need to ignore this guy for a while.

    0
    #162783

    BritW
    Participant

    Not sure ‘we’ are missing the basics, but maybe putting all the responses in one post can help – if this doesn’t do it, please read the new to six sigma link and search fo rthe statistical meaning of six sigma – it will help.
    Sigma (std deviation) and Sigma Level are different, different different.  Don’t confuse the 2.  Sigma is the greek symbol for standard deviation.  Sigma Level is a unitless number of standard deviations that can fit between a mean and the nearest spec limit — in the normal distribution theory it is the Z value.
    Say you have a process with a mean value, spec limits and a standard deviation.  Example:  Mean: 100  Std Dev.: 10  Upper Specification Customer Limit:  110.  Given this, you can fit 1 std deviation between the mean and spec (100 + 10 = 110) – this system operates at a 1 sigma level.
    Now, say you improve the consistency of your process by reducing the standard deviation from 10 to 2.5.  If the mean remains the same, you can now fit 4 (2.5 x 4 = 10) standard deviaitons between the mean (at 100) and the upper spec limit (at 110).  The Sigma Level is now 4.
    In the improvement example, the consistency got better by lowering the standard deviation.  You, in turn, can now fit more standard deviations between the mean and 1 spec limit (increased sigma level).

    0
    #162800

    GKP
    Participant

    I am not convinced . Probably , we are not going to the route of 6 sigma concept . I repeat my question ,if sigma is standard deviation and 6 sigma is 6 x sigma ,why 6 x sigma ,which is 6 times higher than sigma ,is called a world class control with respect to one sigma or half sigma ,which is much lower.
    Regards

    0
    #162801

    GKP
    Participant

    At last , I feel that we are coming close to the answer and my hats off to you .But still , I need a mathematical explanation to understand the inverse proportionality ,as you rightly told. Can you please extend your expertise little further .
    Best regards

    0
    #162802

    Mikel
    Member

    GKP,
    The “six sigma” numbers are meaningless rubbish.  This paper gives an explanation of how the pseudo-maths originated: 
     http://qualitydigest.com/IQedit/QDarticle_text.lasso?articleid=11905

    0
    #162803

    Waskita
    Participant

    GKP
    You are a trully  funny person. No offence but you’re very funny indeed. I just read this topic from the first thread and laugh all the way to the end reading your Qs. All the colleagues in this forum have tried their best to give answer from a very simple way; yet you still don’t understand …not to mention if someone provides some statistical term/formula …you’ll be even more confused.
    Again no offence, but it is you who is the barrier to understand the concept since you don’t have basic statistic knowledge at all. Do a little study first on statistics or if you still prefer a shortcut as you keep on insisting, then come to my home and i’ll explain it to in person with graphics + coffee + crackers …haha. I mean it though!

    0
    #162805

    GKP
    Participant

    It’s one’s perception whether it’s rubbish or religion .Sumant’s message in this concept brings the actual dimension of 6 Sigma ,which is pasted below along with my acknowledgement.
    Regards
     

     
    TOPIC: Re: Six Sigma
    A new message by Sumant was posted in the Discussion Forum.

    Hi GKP,
    your question – “Sigma being standard deviation ,the less it is , better the control .If it’s correct, why six sigma  is better than one sigma”?
    I have made two Sigma’s in 2 different fonts.
    Sigma as standard deviation is not same as Sigma in SIX SIGMA (Here Sigma is known as Sigma Levels), where as sigma as SD known as sigma value.
    Both sigma Value and sigma Level are inversely propotional. When Sigma value is high, sigma level is low and viceversa.
    So when you are saying six sigma, it means your process is operating at six sigma level which is better than one sigma level.
    When Sigma level is higher, process is better, but when sigma value is lower process performance is better.
    Hope I clarified your question.

     
    From GKP
     

    At last , I feel that we are coming close to the answer and my hats off to you .But still , I need a mathematical explanation to understand the inverse proportionality ,as you rightly told. Can you please extend your expertise little further .
    Best regards

    0
    #162806

    GKP
    Participant

    Is it ? With due regards , please go through Sumant’s answer and you will find that the comments given by you on me ,is not that funny ,as you stand now , after reading ,because except Sumant ,none has come even closer to the answer .I will advise you on your own words only

    “Do a little study first on statistics or if you still prefer a shortcut as you keep on insisting, then come to my home and i’ll explain it to in person with graphics + coffee + crackers …haha. I mean it though!”
    Regards

    0
    #162807

    Waskita
    Participant

    :)
    As mentioned, no offence my friend…..My apology for the words chosen in my previous post.
    However; you must be joking when saying Sumant’s comment is the only one closer to the answer. The very first reply from Crazy Guy was short yet sharp, precise, and right to the points as well as others who also tried to assist.
    Anyway, glad to se that you personally think you have understood the answer (at least closer as you said) …..though i still doubt it ;)

    0
    #162808

    GKP
    Participant

    We must understand and maintain the decorum of the forum .My apology too ,to repeat your words .I don’t claim to be an expert but positively gone depth in the subject .Except Sumant , none ,I repeat none ,knew or forgot the basic difference between sigma level and sigma .After Sumant’s answer , I may be able to retrieve the mathematical explanation ,which I may post tomorrow .I repeat ,only Sumant’s explanation, answers the question to the point.
    World is round and we may meet someday .Why only coffee & cookies ? We can have a cocktail ,shading off our little unpleasant communications on the subject. No offense taken ,even your last line being offensive , I’m not returning it back …ha..ha

    “”Anyway, glad to see that you personally think you have understood the answer (at least closer as you said) …..though i still doubt it ;),””
     
    It’s part of the game ,we play, and want to win always ,even if, we know ,we will lose the game. Let’s play win – win .May be , I started the game as a fun only and got entangled by funny and crazy answers .
    Regards

    0
    #162809

    Vikas
    Member

    Standard deviation is the way the data points are spread across the mean using which the ‘Sigma level of a process is determined’
    your statement of Sigma being the std dev is incorrect 
     

    0
    #162810

    GKP
    Participant

    Pass .No comments
    Regards

    0
    #162811

    GKP
    Participant

    Pass .No comments
    Regards

    0
    #162813

    Kambhampati
    Participant

    GKP,
    Sumant did give a good answer but other answers too were correct explanation. “Half knowledge is dangerous”..and you are trying to portray yourself as an expert based on that half knowledge. The problem lies with yu that u did not understand those answers because u lack the basic statistical knowledge. Instead of accepting your short comings you are hell bent on proving others wrong. Just be humble enough to accept your ignorance. People in this forum are experts in the field and have been practitioners. Crazy Guy gave one on the best answers which was very basic and correct. So don’t be judgemental without doing your home work properly.

    0
    #162814

    Yu
    Participant

    Hi GKP,
    A  process with a random natural variation when there is no assignable cause involved spreads itself to three times its std. deviation on either side of the mean. Now it is an assumption that if your specification level is twice your natural variation spread when the process is in control, then you have ample space to play around (read shift of central tendency or accomodate occational outliers) and at the same time not produce any defects.
    This gives a prcess capability (CPk) of 2 and Mr. Mike Harry and Mr. Bill  Smith named this condition of the process as Six Sigma.
    So having a smaller std. Deviation is better whereas one should aim to achieve a process capability of 2, which is six sigma level.
    3.4 DPMO mathematically corresponds to 4.5 sigma, because once you reach six sigma level your process tend to shift 1.5 sigma to either side of the mean in long term.
     
    Thanx,
    SSG
     
     

    0
    #162816

    fake accrington alert
    Participant

    I  believe  you  have  to  review  the  basic  statistics to  underdtand  the  concept,otherwise?

    0
    #162818

    GKP
    Participant

    It’s takes much less time to rectify the mistake than to justify it .Anyway ,thanks for participation and please don’t try to cover it by unpleasent words. I’m closing the topic.
    Regards

    0
    #162976

    sumant
    Member

    GKP,
    Here is the relation between sigma level and sigma value.
    Process Capability (Cp) = (USL-LSL)/(6*SD)
    Where, USL = Upper spec limit
                 LSL = Lower Spec Limit
                 SD = Standard Deviation.
    Lets assume process is centered around mean, in that case,
    Sigma level = 3*Cp = 3* (USL-LSL)/(6*SD)
    Keeping other things constant, Sigma level is inversely proportional to sigma value.
    let me know for any further clarification .

    0
Viewing 41 posts - 1 through 41 (of 41 total)

The forum ‘General’ is closed to new topics and replies.