Does Six Sigma Really Work?

The economic recession has forced corporations to reevaluate its systems and policies, and in this context, the suitability and worth of Six Sigma as a quality improvement tool comes under the scanner.

Six Sigma focuses on process deviations and aims to reduce defects to 3.4 per million opportunities. This assumption of 3.4 DPM is however theoretical, for in practice no process follows the normal distribution model perfectly. The methodology also assumes that the mean drifts over time, and that the maximum process drift is +/- 1.5 standard deviation. This is when some processes may not drift at all, and some other processes may drift more than 1.5 standard deviations. The validity of assuming +/-1.5 the standard deviation for all businesses and all processes is a subject of much debate.

For all the talk of Six Sigma being customer driven, customers do not bother to measure standard deviations. As Gordon Bethune, the CEO of Continental Airlines states, “Our customers don’t measure six standard deviations. They just say ‘I want my bag and I kind of liked the pasta.’ That’s the definition of successes.” True customer orientation requires understanding what the customer wants and adjusting systems and processes to ensure the same, always. Six Sigma’s focus on standardizing deviance in process allows attaining this objective when things work right. However, in an age of uncertainties, where many external variables come to play this always need not hold true.

Six Sigma may help large corporations save costs, but implementation requires significant upfront investment, especially for training. The Six Sigma Academy in Scottsdale, Arizona, run by former Motorola quality experts Mikel Harry and Richard Schroeder, for instance charges $1 million per corporate client. Low budget incremental developmental plans such as Kaizen or Baldrige Award may achieve the same results that Six Sigma provides.

The core of Six Sigma is sensitive to variability in process, and this is in essence, statistical process control in a new avatar. Six Sigma is just one among the many quality improvement tools, which include Deming’s (1982) cycle, Total Quality Management (TQM) assessment methodologies such as Malcolm Baldrige National Quality Award Assessment (MBNQA), the European Foundation for Quality (EFQM) framework and Dorian Shainin’s Statistical Engineering (SE), or even Kaizen.

Top industries such as GE, Raytheon, and Motorola claim to have applied Six Sigma successfully and saved millions of dollars. This however does not mean that every corporation can attain the same result. Edwards Deming himself was a strong critic of one corporation imitating others in quality practices, for what the customer expects differs from business to business.

For instance, customers may value an airline for its smooth and seamless check in, whereas customers may value a coach service provider based on the ability to use alternative routes and reach the destination in the shortest possible time. Some companies such as IBM that tried to imitate the so-called elite Six Sigma companies met with disastrous results.

To sum up, while Six Sigma has its relevance and uses, it is not necessarily the innovative, cost-cutting concept, and a panacea for all ills as touted to be. Being carried away by the hype and mistaking Six Sigma as a cure-all solution is probably the reason why many Six Sigma jokes abound, and many people refer to Six Sigma as “Sick Sigma.”

• Senapati, Nihar Ranjan. "Six Sigma: Myths and Realities." Avici Systems, Inc.
• DMAIC Tools. “What is Six Sigma.” http://www.dmaictools.com/what-is-six-sigma. Retrieved July 27, 2011.

Image designed by N Naseer (author)