The Historical Context
Many have often said that the projection of history can forecast the future. Well, this may be true in some areas of life, but certainly not by considering today’s common notion of the 1.5 sigma shift factor (as associated with Motorola’s Six Sigma Initiative). In retrospect, there was a fork in the road at which point a wrong turn was made by quality professionals and many contemporary Six Sigma practitioners.
By tracing the technical origins of Six Sigma, we will come to understand why the standardized shift factor was vital to certain aspects of Six Sigma. More specifically, we will learn that the shift factor was originally intended for use during the course of product design, not real-time process control (as many falsely believe).
On the subject of learning, Dr. George E. P. Box published a key article in 1976. The article was entitled: “Statistics and Science.” In this article he emphasized the importance of balancing theory and practice. He stated: “One important idea is that science is a means whereby learning is achieved, not by mere theoretical speculation on the one hand, nor by the undirected accumulation of practical facts on the other, but rather by a motivated iteration between theory and practice.”
In light of such wisdom, the 1.5 sigma shift factor was established as a point at which statistical theory was harmonized with the empirical evidence, but done so in a purposeful and rational way. In this context, the shift factor must be viewed as an engineering model, where that model can be used to purposefully and rationally compensate a product design analysis for the inevitable influence of random process centering errors.
Dr. Box goes on to say: “For the theory-practice iteration to work, the scientist must be, as it were, mentally ambidextrous; fascinated equally on the one hand by possible meanings, theories, and tentative models to be induced from data and the practical reality of the real world, and on the other with the factual implications deducible from tentative theories, models and hypotheses.”
In the same article, Dr. Box encourages us to always remember that: “all models are wrong, but some are useful.” Here again, in this context, such guidance is highly applicable to the 1.5 sigma shift factor.
In this sense, the standardized 1.5 shift factor is a first-order approximation and should never be treated as some type of physical law or theoretical constraint that must always be applied in every situation. Again, the shift factor is an engineering model of the first-order, not a precise number that should somehow be used to control and report the behavior of a production process.
Review of the Literature
A cursory review of today’s literature on this topic will reveal that many quality and Six Sigma practitioners attempt to treat the shift factor as a constant when assessing and reporting process capability. For those that attempt such a misguided use of the standardized shift model, they usually wind-up with a nonsensical array performance measures.
Owing to their highly suspect outcomes, they often formulate arguments against the shift factor. Of course, when the outcomes of such misguided applications occur, its much easier for them to lay blame at the door step of the model than accept their own misunderstanding of how, why and when to apply the model.
Without due consideration, the outcomes of such unsuccessful applications are often broadcast throughout the larger Six Sigma community by way of articles, white papers and discussion boards. Unfortunately, they never stop to question the context of their applications. As location is to real-estate, context is to the shift model. If the context of application is inappropriate, the resulting conclusions will likely prove faulty.
Again, the shift factor is only intended for use during the course of product design (and certain benchmarking exercises). The shift factor was never intended for use during course of real-time process control and reporting. Consequently, the current and next generation of Six Sigma and quality practitioners becomes tainted by such seemingly legitimate arguments against the shift factor. The latter points cannot be overemphasized.
From this perspective, opponents of the shift factor are absolutely correct – the shift factor has no place in the world of statistical process control (SPC) or statistical process monitoring (SPM). Even the world renowned Dr. Donald J. Wheeler of SPC fame got it wrong when he labeled the 1.5 sigma shift “goofy.” He simply viewed it from the wrong angle. In short, he had the right answer to the wrong question.
However, on the flip side, the 1.5 sigma shift factor has great relevance in the world of product design analysis and optimization. To fully understand the different contexts and better appreciate their consequential implications, we will survey the technical evolution of Six Sigma. In this way, we can better understand where (and why) the field of quality and Six Sigma “ran off the road” when it comes to Motorola’s standardized shift factor.
The Early Days of Six Sigma
Prior to the innovation of Six Sigma, Motorola was struggling with how to make a quantum change in the quality of its products and services. Several different quality improvement goals were established and then latter elevated. Thus, the birth of Six Sigma.
In the beginning, there were only a handful of us (at Motorola) that were directly involved in the initial formulation of Six Sigma (1982-1985), chief among which was Mr. Bill Smith and this author – see table on page 83, “How Management Innovation Happens,” MIT Sloan Management Review.
During this period of time (1982-1985), we tossed around many ideas and approaches that could be used to achieve a Six Sigma level of quality by 1992. At day’s end, our developmental goal was to create a methodology that could link product reliability targets to design tolerances and process capability; and do so in a more predictive manner.
In this way, we could “design in” quality rather than becoming masters at “detecting and fixing” defects. Thus, we could greatly improve customer satisfaction while concurrently reducing the company’s total cost structure. It was during 1986 when Motorola officially adopted Six Sigma. Correspondingly, this author published the first definitive essay on the subject: “The Nature of Six Sigma Quality,”
This booklet initially served as the definitive source for Six Sigma. It also presented and discussed several innovative manufacturing and engineering concepts. According to Motorola University Press, over 500,000 copies of this booklet were printed and distributed throughout the world.
As Six Sigma was still in a fluid state until about 1987, several grass-root initiatives got underway across Motorola. The aim of such initiatives was to further solidify the form, fit and function of Six Sigma, as well as to find ways it could be expanded in terms of scope and depth of application. Over time, the cream of such grass-root efforts rose to the top.
As a matter of informal protocol, the top technical ideas and innovations from around the company were often first passed through a local filter to evaluate things like feasibility and utility. After this, the surviving ideas and innovations made their way to one or more of the various corporate oversight and policy groups, like the Motorola Corporate Quality Council and Motorola Science Advisory Board.
Of course, the purpose of the corporate-level filter was to review and adopt the best-of-the-best, so to speak. After passing through this filter, the top ideas were passed on to the Motorola Training and Education Center (latter designated as Motorola University in 1989). Essentially, Motorola University would package and distribute the new knowledge in the form of books, manuals and training programs.
At the end of the line, Motorola executives, managers, engineers, technicians and general employees would make use of the new knowledge (to varied degrees of application). Naturally, the feedback from such field applications was passed back through the aforementioned filters. In this way, Motorola was able to quickly deploy and implement new technical knowledge to the benefit of its stakeholders.
Of interest, 1988 was a pivotal year for Motorola and Six Sigma. During this time, Dr. Ron Lawson and this author published our initial work on the subject of Six Sigma Producibility Analysis and Process Characterization, which quickly migrated to the US Navy. Also during 1988, this author worked in conjunction with Mr. Reigle Stewart to publish a textbook and supporting software on the subject of Six Sigma Mechanical Design Tolerancing.
The crown jewel for this year was Motorola winning the first Malcolm Baldrige National Quality Award, for which Six Sigma was credited as playing a major role.
The Center of Development
With the aim of consolidating and centralizing the grass-root efforts, this author prepared a formal proposal in late 1989. The proposal was submitted to the senior executive team of corporate Motorola in January of 1990. The proposal was subsequently approved by Mr. Bob Galvin (then CEO and Chairman of Motorola).
To implement the proposal’s intent, the Six Sigma Research Institute (SSRI) was formed and operationalized in 1990 by this author and executive. Through this strategic thrust, Six Sigma began to find its way into the professional head-space of executives, managers, engineers and technicians. In 1992, this executive founded the Six Sigma Technical Institute (SSTI) and launched its first program, which was the technical corollary of the Motorola Management Institute (MMI)
In about the same timeframe Six Sigma managed to secure its place within the MMI curriculum. Then in 1992, under the direction of this author, SSRI began creating the BlackBelt infrastructure at Motorola, Kodak, Texas Instruments, IBM, and Digital – all of which were members of SSRI.
In short, Six Sigma was quickly changing the company’s perspective of quality. Before Six Sigma, the company mindset was built around the “Business of Quality.” After solidifying Six Sigma, the mindset switched to the “Quality of Business.” Indeed, this was huge philosophical shift with many implications.
An excellent summary of Six Sigma’s early times appeared in a Quality Digest article prepared by Dr. John S. Ramberg, a prestigious engineering professor at the University of Arizona. Dr. Ramberg’s highly informative article was entitled: “Six Sigma: Fad or Fundamental?”
Owing to his direct involvement with Motorola on this subject, Dr. Ramberg’s narrative provides a crisp, clear and highly insightful look at the technical side of Six Sigma, as well as the early role it played at Motorola. Of particular interest, the reader is strongly encouraged to read his sidebar discussion: “Origin of Six Sigma: Designing for Performance Excellence.” Another highly accurate chronology of Six Sigma’s history and evolution is provided by Process Quality Associates, Inc.
The Solid State
By 1993, the Six Sigma program started to build significant momentum within the mainstream of Motorola, as well as several other companies. From this perspective, it’s easy to see that Six Sigma had transitioned from a liquid to a virtually solid state.
Elsewhere in the company, we were steadily applying the Six Sigma principles and methods to design engineering problems, as well research and development activities. Even seemingly diverse areas such as the corporate law department and cafeteria started using Six Sigma as a means of improvement.
In terms of tools, SSRI had developed and rolled-out an electrical design analysis and optimization methodology for both analog and digital circuits. Also in the toolbox was a statistical tolerancing system for mechanical design engineers. In short, the Six Sigma tool box was getting bigger and the applications were many, especially in the area of design engineering.
Also about 1993, Motorola’s quality engineers were consistently using Six Sigma methods in the design and development of new manufacturing processes and factories. In parallel to this, reliability engineers began systematically working with product designers to reverse engineer certain product component specifications based on a desired reliability model.
For example, a reliability engineer might elect to start with the targeted instantaneous failure rate of a product. From here, the engineer would reverse compute the pre-screen defect rate which, in turn, would be rationally allocated back to the product system components.
From this information and data, the quality engineer would develop an appropriate process capability model for both the centered and shifted cases. In this manner, the quality engineers, reliability engineers and product engineers would work together as a team to concurrently design a product that would be robust to process variations in both bandwidth and centering. Such is the Six Sigma way of thinking.
Unfortunately, it was during 1993 that Mr. Bill Smith passed away in the company cafeteria. His achievements at Motorola were numerous, with Six Sigma being his crown jewel. Without saying, his loss represented a setback in the momentum toward Six Sigma, but through his wisdom and teachings, the continuance of Six Sigma was assured.
By 1994, the principles and methods of Six Sigma had even pierced the veil of software engineering. At about this time, the core concepts and practices of Six Sigma were being slowly integrated into the areas of financial risk assessment and abatement. Overall, Six Sigma was rapidly moving toward its destiny as a world-class system of business management.
Business Phone: 480.515.0890
Business Email: Mikel.Harry@SS-MI.com
Copyright 2013 Dr. Mikel J. Harry, Ltd.