[fine69]

Originally Posted by Dieseltuned

I am still in the lookout for SSGB course which includes a project. Thinking of registering with KPMG atleast for the training.

Regards
Dieseltuned

No course includes a project. Third-party institutions provide you with training and training certificate. After you submit your project, they evaluate (supposedly ) and give you the certified certificate. This process is same for all institutions.

For the project being submitted by you, certain institutions ask for a proof on company letterhead that you actually led the project on your own along with the project presentation. Some like ISI don't care about it and would just want you to submit the story in a word document, no company letterhead or anything.

After all, its all business, in case institutions get too fussy about evaluating whether a project is genuine or not then they end up losing customers.

If you would only like a 'SSGB Certified' stamp on your resume then ISI is cheap and best. In case you would like after sales support (with their forums etc.) then private institutions are good.

ISI training is crappy while pvt institutions (almost all of them) would give you decent material along with ok training on concepts, usage of Minitab etc. Mind you, ISI doesn't even touch Minitab in their curriculum while no pvt institution would provide training without Minitab. So depending on your objective you'd have to decide.

Let me also say that I was approached by a somewhat reputed institution to provide GB trainings on my free days and the guy who interviewed me didn't know half of the subject himself. He was an MBB.

[Dieseltuned]

Originally Posted by fine69

No course includes a project. Third-party institutions provide you with training and training certificate. After you submit your project, they evaluate (supposedly ) and give you the certified certificate. This process is same for all institutions.

For the project being submitted by you, certain institutions ask for a proof on company letterhead that you actually led the project on your own along with the project presentation. Some like ISI don't care about it and would just want you to submit the story in a word document, no company letterhead or anything.

After all, its all business, in case institutions get too fussy about evaluating whether a project is genuine or not then they end up losing customers.

If you would only like a 'SSGB Certified' stamp on your resume then ISI is cheap and best. In case you would like after sales support (with their forums etc.) then private institutions are good.

ISI training is crappy while pvt institutions (almost all of them) would give you decent material along with ok training on concepts, usage of Minitab etc. Mind you, ISI doesn't even touch Minitab in their curriculum while no pvt institution would provide training without Minitab. So depending on your objective you'd have to decide.

Let me also say that I was approached by a somewhat reputed institution to provide GB trainings on my free days and the guy who interviewed me didn't know half of the subject himself. He was an MBB.

Thanks a lot sir,

That pretty much sums up the situation in the industry today

Will keep this thread posted on what we decide.

Regards
Dieseltuned

[Samurai]

I am trying to get a mathematical understanding of six sigma. But I am a bit confused about the possible ±1.5σ shift in mean.

Let's say I am making 1 meter tall walking sticks. Of the 1000 sticks I make, shortest is 991mm and the tallest is 1009mm. That is within accepted tolerance for this product.

That lets me estimate the SD as 18/6 = 3mm. Here we talking 3σ process.

How does six sigma apply to the above situation? What will be the changes to σ, μ and range, and why ±1.5σ shift in mean is acceptable?

[Samurai]

Originally Posted by Samurai

How does apply six sigma to the above situation? What will be the changes to σ, μ and range, and why ±1.5σ shift in mean is acceptable?

Since I haven't received any reply so far, I let my imagination run wild.

If this process become six sigma compliant, the new σ = Range/9 or 18/9 = 2mm. Since μ can deviate by ±1.5, the mean could vary from 997 to 1003.

Then 997 - 3σ = 997 - 6 = 991mm
1003 + 3σ = 1003 + 6 = 1009mm

The range remain the same, Mean (μ) can vary between 997 to 1003, and SD (σ) changes from 3mm to 2mm. Defect rates change from 0.27% to 0.00034%. This is the effect of moving a process from 3σ process to six sigma process. Does this make sense?

[Samurai]

While I was waiting for green/black belts clarify my thoughts, I discussed this with another BHPian. He wondered why I assumed Range/6 = σ, and what is the meaning of mean shift by ±1.5σ.

So I am further spit-balling.

In the walking stick example, I had mentioned that the lengths 991mm-1009mm are limits of the tolerance, and that the shortest stick is 991mm and the longest stick is 1009mm for this sample. This is either perfect zero defect or near zero defect scenario. But taking the worst case scenario, what process comes closest?



1σ Process: At least 31% walking sticks will be outside of 991-1009mm range. So this can't be it.
2σ Process: At least 4.5% walking sticks will be outside of 991-1009mm range. So this can't be it either.
3σ Process: Only 0.27% walking sticks will be outside of 991-1009mm. So this could be the worst σ value we could consider.

That is why I assumed 3σ process, and got σ = Range/6, or 18/6 = 3mm.

But there is one major problem with 3σ process, it has no tolerance for mean shift. As long as the mean is at 1000mm, everything is fine. However, after some wear and tear, the machine might shift the mean away from 1000mm. What if it starts making sticks of mean length of 1002mm, while the σ remains at 3mm. The ±3σ range now shifts to 993mm-1011mm. The 3σ deviation on the higher end is now outside of specified tolerance.

The six sigma allows for ±1.5σ deviation in the mean value itself. That means the machine can shift the mean from 1.5 times σ in either direction. But that is not possible while keeping σ at 3mm. At 3mm, the mean can shift from 995.5mm to 1004.5mm, if you add another 9mm (3x3mm) for 3σ deviation, we are looking at 986.5mm to 1013.5mm. Too many rejections.

If the machine is replaced or improvised to provide σ = 2mm, then the ±1.5σ mean shift will be between 997mm-1003mm. The 3σ deviation will be 6mm (3x2mm) in either direction, restricting the extremes to 991mm-1009mm. While the range has remained same, due to decreased σ, the probability of sticks falling outside of tolerance range would have gone from 0.27% to 0.00034%.

PS: What happens if distribution is not normal? Is six sigma still applicable?

[revvedup]

Step 1 - I believe you need to start with the mathematical fundamentals first, understand how standard deviation or Sigma is defined and how it is relates to the mean. While you have derieved a way of finding out the acceptable standard deviation for a process to remain within spec, it is by no means a way to calculate the standard deviation of a sample or a population.

Please find the relevant mathematical concepts explained here

http://davidmlane.com/hyperstat/A16252.html

http://www.dummies.com/careers/proje...for-six-sigma/

Step 2 - it is important to understand that a six sigma process is one in which the distance between the mean and a spec limit ( higher or lower ) is six standard deviations. Hence the probability of the proces producing something that it is out of spec is quite low, i.e, 1-99.9999998% Here
99.9999998% is the percentage of process outputs or values that will fall within the mean and six standard deviations, as compared to 99.7 % within three standard deviations or sigma.

Explained in more detail here http://www.howardgitlow.com/definitionsofsixsigma.htm

Hope this helps.

[Samurai]

Originally Posted by revvedup

Step 1 - I believe you need to start with the mathematical fundamentals first, understand how standard deviation or Sigma is defined and how it is relates to the mean.

Why are you assuming I don't know that? This is an hypothetical scenario, I can't measure each hypothetical walking stick and calculate the actual standard deviation using the formula. Hence the approximate method.

Originally Posted by revvedup

Step 2 - it is important to understand that a six sigma process is one in which the distance between the mean and a spec limit ( higher or lower ) is six standard deviations.

You mean six standard deviation from the mean in each direction? ±6σ would give you 2 defects per billion. I don't believe such a process has been ever achieved.

My understand of six sigma is ±3σ or 3 standard deviation from mean in either direction, while allowing for 1.5σ shift of mean in either direction. That gives 3.4 defects per million.