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Six Sigma MethodologyThe Six Sigma methodology is made up of five steps or phases. These five steps in order are:
1. Define Before we go into detail about the phases, we first need to understand when this structured approach should be used in problem solving. There are, of course, many different problems in the world (and they make the world quite an interesting place). However, the problems all range in complexity. There are simple problems such as, "My pen doesn't work." There are also more complex problems such as, "My bottleneck machine breaks down every 2 weeks." For the first problem, you really do not need to use the Six Sigma methodology. This is a problem where gut feel or intuition can be used and there are not many variables or factors that could affect your pen. It may be the ink or it could be the ball. Either way, this problem should be easy to solve. Better yet, it may just be better to throw away your pen and buy a new one as the consequence of this should not be too big (unless you are using a Mont Blanc). The second problem, however, is much more complicated. This is a bottleneck machine after all, so if it breaks down, the consequences can be quite brutal. Moreover, it might not be wise to throw out an expensive machine and replace it without some investigation. Most production machines have many parts - both moving and still - in them and there are many different factors and variables that can affect how they perform. A problem like this could use the help of the Six Sigma methodology and the DMAIC phases. Of course, the examples given here are at two extremes. But many companies spend too much time going through the DMAIC phases when really a good kick or shake could solve the problem. They do this because they want to show that they use Six Sigma for everything. Or employees want their projects to be successful and choose a simple problem to solve…one that they may have a good idea of what the solution is already. Trust us! Time and resources are being wasted if you deploy the Six Sigma methodology on simple problems. The DMAIC phases should only be used for problems where the solution to the problem is unknown and the problem is more complex.
First, let's talk about outputs. Outputs are what you desire from any process. If you take a look at our jeans production example from our Six Sigma tutorial, one of the outputs desired was "Jeans with 32 inch waist size". The actual output here is "waist size" and the desired value for this output is "32 inches". This is what you or your customer require from your process. Of course, one process can have many outputs. Inputs are the factors that could have an effect on your output. For the output of waist size coming off a jeans production line, there could be many different factors that affect this. It could be the machines, machine settings, the operators, the room temperature, the type of denim, the type of wash, the temperature of wash…and so on. The easiest way to think of an input is…if the setting of this input was changed, would it change the value of the output? For example, if we changed the temperature of the wash, would it change the shrinkage and make the waist size larger or smaller? The Six Sigma methodology does precisely this for you. For an output, there will usually be only about 3 to 5 inputs that have a SIGNIFICANT impact on it. When you start in the Define phase, however, you may have over 20 to 30 factors (inputs) that you suspect could have an effect on the output. Take the jeans example above. If we wanted to go on with the list possible factors, we could probably have about 20 of them. As you go through the DMAIC phases, the tools in each of the phases help you eliminate and filter out the factors that do not have a significant impact on your output.
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