Six Sigma and why it fails in the real world

have to post this. Apologies if it ruffles the Black Belts among you but this is precisely why clients aren’t interested in the boffin levels Sigma go to. They want a continuous improvement culture not the equation to calculate the trajectory of Apollo13…..I mean, it’s for a call centre environment, one of the most chaotic set of processes. A pragmatic approach is really all that’s needed here yet sometimes we are so caught up in our own ideals we fail to see that a simple answer might be the best.

This appeared on LinkedIn today:

I Need a help to solve this Six Sigma Case, for many it might be easy
Case:There is a Call Center process in which CTQ is Customer Response Time.If Customer Response Time is more than >60sec then its a defect.In this Case opportunity will be 1.Suppose there are 300 Calls and out of that 123 call Response time is >60 sec(This is defect) and opportunity is 1 then my Sigma value will be 1.727.This value came by this Formulae
process Sigma = NORMSINV(1-((Total Defects) / (Total Opportunities))) + 1.5 and DPMO is 410000, this value came by this formulae

Defects Per Million Opportunities (DPMO) = ((Total Defects) / (Total Opportunities)) * 1,000,000

Question is, Can anybody tell me from this case how can i get bell Curve.How i should calculate USL and LSL value.How i will draw this Bell Curve in a excel.Waiting for all your master response?

An excellent response from a friend over at the BPM Nexus and paraphrased here sums it up:

“…at the end of the day if you produce a bell curve telling me the USL and LSL for my call centre, along with the number of defects per million and a sigma value of 1.727, is this really a useful measure? More to the point, what can I – as a business person – do with it?”


2 responses to “Six Sigma and why it fails in the real world

  1. While it’s necessary not to get lost in the details and miss the forest for the trees , a good six sigma practioner will know how to interpret and communicate the result as well. I would say statistical measures provide a tangible and measurable parameter to improvement projects. Yes, a business person may not need to understand the “formula” , but the interpretation from such an analysis would be invaluable. A Black Belt will not tell the client ” the USL and LSL for my call centre, along with the number of defects per million and a sigma value of 1.727. Rather , a good BB would use these numbers to interpret the situation and recommend solutions from tangible measurments.

    Coming back to the LinkedIn question- it was a technical question – I’m not sure how you interpret that as a failing of six sigma?

  2. We can’t get buried in statistics and lose sight of what we are really trying to accomplish. Math and stat techniques can be obtained from math books, but business sense comes from experience. I agree with Samita, on her point about communicating six sigma results. I think everyone can agree that if you start talking about USL and LSL and other technicalities you can quickly lose with the business people. Also, I don’t see this as a Six Sigma failure and companies like GE, Dupont, Motorolla and others would agree with me.

    Good real world post – similar situations happen quite often.

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