Let's start with a few "facts" which you can learn during the Six Sigma course...
Six Sigma was created in the 80s’ by Motorola employees: Bill Smith and dr Mikel J. Harry developed further in General Electric in the 90s’ led by Jack Welch.
Many paperwork, courses and websites describe Six Sigma as a continuous improvement programme that mainly aims to reduce variation and improve quality.
SIX SIGMA – WHAT IS IT?
Six Sigma is a disciplined, evidence-based, enterprise-wide TOOL that recognises problematic business areas, defines improvement solutions and projects, determines and implements data-driven, breakthrough results in a predictable and repeatable manner that improves business outcomes.
In a nutshell, we can define Six Sigma with three words - Facts, Numbers and Data.
“Six Sigma is a quality program that, when all is said and done, improves your customer’s experience, lowers your costs, and builds better leaders.”
Jack Welch (GE)
SIX SIGMA AS A METHODOLOGY - As a methodology, Six Sigma provides an organised, strict, repeatable approach to assessing and resolving complex challenges through the framework called DMAIC or DMADV/DFSS.
DMAIC
DMAIC is an integral part of any Six Sigma programme and provides a standardised project framework to solve complex issues which you cannot resolve with standard problem-solving tools. In a nutshell, DMAIC stands for:
DEFINE PHASE
Understand the problem and the full scope of the project.
Understand Stakeholders' relationship.
Understand customer needs.
Understand SMART Objectives.
MEASURE PHASE
Understand the current process (get an accurate picture of what is really happening).
Collect data from the current process.
ANALYSE PHASE
Interrogate the data from the current process in order to find the root cause and poor process performance.
Explore – Generate a hypothesis – Validate.
IMPROVE PHASE
Understand the root cause of problems.
Have a clear list of improvement opportunities (with alternative solutions).
Find the best solution.
Pilot and validate your solution.
CONTROL PHASE
Sustain improvements in the long term.
Create a control plan & system where everyone can see whether the process is stable and capable.
DMADV/DFSS (Design For Six Sigma)
The primary Six Sigma methodology objective, DMAIC, is to improve existing processes, so it requires a process to be in place and functioning. On the other hand, DMADV/DFFS were created to design new processes and product solutions. Over time, many DFFS derivatives have been made (with different phase names); however, the objectives and tools used within the steps are still the same.
Six Sigma did not create any new tools – it uses the appropriate existing ones that make all the difference. All business decision-making is based on hard data, numbers and facts (not opinions).
Six Sigma links the business output of the process to the customer’s expectations by reducing errors and variation within the process (staying within limits defined by the customer will yield significant returns).
UNDERSTANDING SIX SIGMA
To understand the concept of Six Sigma, you need to get familiar with an equation.
Y=f(x) is a fundamental concept of the Six Sigma approach to problem-solving and, in simple terms, can be described as ’cause & effect’, where Y = output which is dependent on the inputs - ‘X’s’ (the observed output is a summary of all the inputs). If the X’s determine how the Y performs, we need to find out which X’s are critical and significantly impact our Y.
Of course, almost every process contains many variables (‘X’s). However, our output is not affected equally by all of them. Six Sigma helps you separate these “vital view” variables affecting your input from “trivial many”.
Six Sigma Roles & Responsibilities
Six Sigma concept created many roles and responsibilities for successfully implementing the projects.
Every person is trained to be able to understand and perform the duties of their position. The roles which we could distinguish are:
Executive Leadership - any project deployments should be driven from the top by executive leadership (those deployments driven by executive management are much more successful than those that are not). The executive leadership owns the vision for the business, provides sponsorship and sets expectations for the results from programmes like Six Sigma.
Champion/Process Owner - Champion’s role is to identify and select the most meaningful projects to work on; they guide the Six Sigma Belts and open the doors for the belts to apply the process improvement techniques.
Master Black Belt – a technical expert and mentor of Black/Green Belts, support Champion. Influence change, motivate others, provide training and support, teaching others the practices and tools.
Black Belt is a Project Team Leader and Six Sigma expert who works cross-functionally on complex projects that require a significant focus to resolve.
Green Belt - Green Belts are capable of solving problems within their local area of control. Most of the time, they remain in their current positions but apply the concepts and principles of Six Sigma to their job environment. They usually address less complex problems than Black Belts.
Yellow Belt – typically has a basic knowledge about Six Sigma and supports Black and Green Belts. They should be capable of defining processes, solving problems associated with their work responsibilities, and implementing and maintaining the gains from improvements.
SIX SIGMA NAME
The name ‘Six Sigma’ (etymology is based on the Greek symbol “sigma” or “σ “) is derived from the data bell curve used in statistics as a reference to the statistical measurement of process variation from the process mean (average) or target, where one sigma = a single standard deviation from the mean.
The number Six refers to the Sigma capability of the process, which is the ultimate goal of every process, according to the orthodox Six Sigma dogmatists. It equals 3.4 defects per million opportunities (more details below).
SIX SIGMA CONTROVERSY (a quick brief)
3.4 Defect Per Million Opportunities (DPMO)
Famous 3.4 DPMO, an enigmatic goal of 6 “sigma-level/score” (sigma level is commonly used measure in Six Sigma of process capability that represents the number of short-term standard deviations between the centre of a process and the closest specification limit).
According to one of the greatest statisticians, Donald J.Wheeler, the whole concept of Six Sigma is “a bit goofy”.
“Six Sigma defects per million opportunities:
- Are incomplete, being based on the cost of scrap & rework (this number is ignoring the cost of using conforming product).
- It applies a standard conversion in a non-standard way to obtain values that have no basis in reality and no mathematical credibility.
- It treats the amount of drift you will occasionally experience in the best-case scenario as the worst that can happen in the absence of a mechanism for detecting process changes.
- It is used in reverse to convert an observed level of nonconforming product into a pseudo capability index for a process without any consideration of process predictability or the lack thereof.
- DPMO values are merely data divided by an assumption, and are therefore totally subjective.”
Donald J.Wheeler “The Six Sigma Zone”
Sigma shift & drift (+/-1.5 sigma)
According to Dr Tony Burns, Sigma shift & drift invention has been introduced by Mikel Harry, based on a 1975 paper by Evans, “Statistical Tolerancing: The State of the Art. Part III. Shifts and Drifts” (Evans took his “1.5” number from 1962 paper by Arthur Bender on tolerances in the height of a stack of discs).
Mikel J Harry addressed the issue in his book “Resolving the Mysteries of Six Sigma” (Harry, 2003).
“Many practitioners that are fairly new to six sigma work are often erroneously informed that the proverbial “1.5σ shift factor” is a comprehensive empirical correction that should somehow be overlaid on active processes for purposes of “real time” capability reporting. In other words, some unjustifiably believe that the measurement of long-term performance is fully unwarranted (as it could be algebraically established). Although the “typical” shift factor will frequently tend toward 1.5σ (over the many heterogeneous CTQ’s within a relatively complex product or service), each CTQ will retain its own unique magnitude of dynamic variance expansion (expressed in the form of an equivalent mean offset.”
Mikel J Harry “Resolving the Mysteries of Six Sigma”
In a nutshell, Dr T. Burns claims that:
A Six Sigma process can't produce a good quality product with its 1.5 sigma shift in the mean.
When a process drifts or shifts, it will produce points outside control limits which means that the process is out of control. Out of control processes may shift by ANY amount (not only 1.5 sigma). These processes are unpredictable and may produce ANY amount of errors, no matter where specification limits are set.
You can read about it in more detail here.
On the other side, we can find publications like Tim Akerman's – "Where is the evidence of sigma shift", which tries to explain the sigma shift & drift mechanism.
The very high failure rate of Six Sigma change initiatives
According to Heriot-Watt University research (Sony, M, Antony, J, Park, S & Mutingi, M 2020, “Key Criticisms of Six Sigma: A Systematic Literature Review”):
A Fortune article stated that of 58 companies that announced Six Sigma implementation, 91% had trailed S&P 500 since then.
In a study in the healthcare sector, it was estimated that 62% of Six Sigma initiatives have failed (54% of the companies do not intend to implement Six Sigma).
Around 60% of all corporate Six Sigma initiatives failed.
Many tremendous success stories of Six Sigma saving big money are without evidence and not recorded properly.
No central Body Of Knowledge/Owner governing Six Sigma certifications
Not many people know that THERE IS NO GOVERNING BODY that sets standards, grants and manages Six Sigma certifications. What does it mean in practice? Anyone can create their certification standards as they want; anyone can do training and offer accreditation, so Six Sigma could be pretty much whatever they wanted it to be.
Can you see the trap?
This causes a lot of variation in the level of skills and knowledge between certified people and training providers. The whole CI training industry is packed with nonsense and utterly useless knowledge. It floods the business world with many unskilled “experts” who dilute the “CI knowledge”. Did I mention about huge prices of Six Sigma/Lean Six Sigma courses?
Six Sigma is not equal to Statistics
Every training provider will agree with the statement above. However, at the same time, during 10 days course, almost every training provider will try to teach you ANOVA, the Kruskal-Wallis test, Bartlett’s Test, Chi-Square, Box-Cox Transformations, and so on.
“Analysis of variance, t-test, confidence intervals, and other statistical techniques taught in the books, however interesting, are inappropriate because they provide no basis for prediction and because they bury the information contained in the order of production. Most, if not all computer packages for analysis of data, as they are called, provide flagrant examples of inefficiency.”
Dr Edward Deming (Out of the Crisis. - Dr Deming. 1986)
10 days Six Sigma/Lean Six Sigma course cannot teach you correct usage or give you even a good understanding of all the statistics squeezed into these courses.
Most training providers are trying to fill in the gaps and make more money from long training courses teaching complete garbage without relevance to processes. So if you plan to get one of these courses or send your employees to it, double-check the course content: if you cannot see anything about PDCA, 7 basic quality tools, Deming or Shewhart – this should be a red flag.
In Summary
From one side, I see Six Sigma as a fancy problem-solving method on "statistical" steroids. When you strip it off from all useless nonsense, sigma levels, etc., you end up with a nice structured DMAIC framework, which is just a re-branded PDCA cycle!
However, on the other side, I am thankful for my Lean Six Sigma course as it opened the door to new possibilities and gave me a broader view of business problems.
Does Six Sigma really work? Well - it worked for me.
It worked for me when I combined the Six Sigma tool with Lean and had full support from Executives (I never used Six Sigma in isolation).
However - retrospectively - today, I would get the same results with much easier problem-solving methods in a shorter time period (another Six Sigma downside - very long project life cycle time).
Will Six Sigma work for you? It depends. Do you need it? Not necessarily. Most of your problems could be resolved with much quicker and more straightforward methods (99% of your issues do not need Six Sigma at all).
Do you need to send your employees to the Six Sigma/Lean Six Sigma course? Again, it depends. What do you want to do with it? Do you want to implement real changes within your organisation, or do you want to have a useless LSS Black/Green Belts army with fancy pictures and paragraphs on your social media/website?
I could be mistaken; perhaps I'll need to use this approach to resolve some challenges in the future. However, for the time being, I strongly believe we have much better and more accessible tools to solve any problems.
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