Monday, May 17, 2010

Whats the difference between flavors of six sigma?

Six Sigma for Manufacturing; Six Sigma for Healthcare; Six Sigma for Public Sector; Six Sigma for Education.

There's a lot of marketing materials out there hyping the specialty classes and programs for Six Sigma or Lean for a particular industry sector or application. So, what is really different between these different approaches? In short-Nothing.

Lets start with what Six Sigma is and what it is not. Six Sigma is a universally applicable logic based improvement process, it is not specific to manufacturing environments only. Six Sigma is flexible in the use of specific tools for a given problem, it is not so flexible that the logical problem solving process can be avoided. Six Sigma is a scientific method of discovery, it is not a substitute for knowledge.

One thing that may not be universally recognized is that the specific tools that are endorsed and needed to make the six sigma method work effectively are not unique to six sigma. The early practioners of Six Sigma did not invent Gage R&R, Capability Analysis, Process Flow Diagrams, Brainstorming, Regression or Designed Experiments. What they did do was recognize how those tools could add value and strengthen the six sigma method. Why is that important to understand? because understanding that the "inventors" of six sigma borrowed good tools from other areas where they were already in use informs us that we also can adapt tools and apply them in the six sigma method without violating the 'spirit" of the method. For instance; the generally accepted statistic used to express capability in a six sigma project is the Z score, however if you have a transactional of office process that you are working on and continuous data is not available to derive a Z score, thats OK. Just count occurences of your defect regardless of what it is (time, errors, missed deliverables, rework) and report a percentage of failure against the requirement. That's the same thing in "spirit" as a  Z score. Some dogmatic practitioners might insist that the only acceptable metric is a Z score. I assure you this is not correct, what is required is that we measure our baseline capability against the requirement of the process (specification) and express that in some appropriate way.

The other area of flexibility in the six sigma method is in the area of specific process steps that apply. I have led and mentored many project teams and in some of those cases we have had to abandon efforts to complete certain steps because the process we were working on did not lend itself to effectively completing that particular step. In other cases there have been steps that were not needed. One of the typical steps that some teams struggle to complete is the Gage R&R requirement. In some cases it is not practical or necessary to conduct a proper Gage R&R but it is always necessary to ensure that the data is reliable. See this post for a further discussion fo Gage R&R. The step that most often gets skipped is the Designed Experiment step in Analyze. many times this step is skipped intentionally and quite properly because earlier analysis of historical data via regression has produced a conclusive list of reliable root causes and no experimentation is needed to confirm or screen these root causes. If you know from historical data what needs to be fixed, why waste time and money on a confirmation experiement. Conversely, recognizing that your suspected root causes are weakly correlated to the problem should drive the design of an experiment to determine conclusively what the causes are. Of course in an office or transactional project, a designed experiment may not be possible.

Six Sigma is a flexible, universally applicable process improvement method that follows the logical thought pattern of; Define the problem, Baseline performance, Discover root causes, Implement improvements, and Standardize the new process. These concepts apply to any process, anywhere in any professional setting. What is required to use the method successfully in any setting is an understanding of the improvement process, the reasons why each step is important, how all of the steps fit together, and a concerted effort to apply each step. Finally, if you are doing a six sigma project and have used a particular tool effectively in the past, there is no limitation to the use of new tools within the six sigma process. if it works for you and is effective at helping the team move forward, use it.

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