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Randomization And Six Sigma

Aug 17, 2007
Simplistically speaking, randomization in Six Sigma and any experimentation can be likened to surprise visits which help expose undetected lurking flaws in any place you may want to think of. Sometimes it pays to run random checks, even on highly standardized procedures, which eventually detect factors running over the length of the experiment in an uncontrolled manner.

As a general rule, industrial experiments are run in split plot modes for expediting purposes and for reasons of governing and monitoring. The experiments let the effects of the split plot factors for estimation more precisely as opposed to the effects of the whole plot. This turns out to be unfortunate when the focus lies in whole plot factors.

Randomization in Experimental Design

The importance of conducting randomized research experimentation arises from the need for convenience in controlling the extraneous variables. The strikingly out of the ordinary variables which otherwise would not have given ways to measure would now spread out evenly or average out across the experimentation conditions, when randomized.

Statisticians favor a completely randomized testing environment for sound theories. But the engineers who are running the experiments often neglect restrictions like the split plot experimentation and get caught unaware of the associated risks. On their part, statisticians too, fail to understand that the restrictions on randomization do not result in reduced information than a whole plot randomized design.

Further Justification of Need for Randomization

What makes things worse is combining multiple factors and their levels can make things very large a task to handle. In order that the things are simplified, some informed deductions become imperative to understand which factors will generate the most pertinent data that helps provide information for substantial results. The experiment must be randomized at the sequential run level.

It must be understood that restriction on randomization and replication of experiments leads to complex designs having a number of fatal experimental errors. Because it crucially allows external factors equal chances to affect each run. The expected results are difficult to have with non-randomized experiment, the reason being the risk of external factors acting in a predetermined manner, and adding noise to the response.

It is desirable for engineers to run experiments in multiple sets (called replication). This can be depended upon to provide greater confidence in evaluating the results, as you are flush with abundant data. Depending on budgetary flexibilities, it is desirable to have more of these replicated experimentations for apparent reasons.

Handling Randomization By Black Belts

Six Sigma Black Belts must know the difference between different types of models of experimentation. For the experimentation to be effective and result-producing, the Black Belts are the crucial links and must understand the concepts of randomization.

In cases where background variables can't be eliminated totally, another concept called blocking can be used. It spreads the variables across the experiment.

Randomization has its root in science just how Six Sigma draws its strengths. The interpretation of results in split plot mode must be done carefully to avoid inherent pitfalls.
About the Author
Tony Jacowski is a quality analyst for The MBA Journal. Aveta Solution's Six Sigma Online offers online six sigma training and certification classes for lean six sigma, black belts, green belts, and yellow belts.
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