Six Sigma versus Lean: What's the Controversy? What the Difference?

Many professionals ask "What is Six Sigma?", some ask "What is Lean?", and of course still others ask "What is Lean Six Sigma?" As it turns out, these approaches address similar problem sets but attack them differently. Here is a look at what they are, the similarities, the difference, and the synergies.

The difference between Lean and Six Sigma can be summarized as follows:

Six Sigma = Reduced process variation
Lean = Improved process flow

Let's take a look at each.

What is "Lean"?
In the practice of "Lean", the focus is on breaking down processes to the "bare bone essentials", hence the name "lean". The Lean approach to waste is that "Non-value added is waste". Hence, the proactice of Lean has as its central goal to segregate waste from value in processes, and eliminate the waste and non-value added.

The typical method for practicing Lean is to do the following:

1. Identify Value
2. Define Value Stream
3. Determine Flow
4. Define Pull
5. Improve Process

The focus of Lean is on Process flow. Tools used for the practice of Lean are oriented to visualization, and include tools like Microsoft Visio.

What is Six Sigma?

In the Six Sigma approach, the view on waste is that "Variation is waste".

In practicing Six Sigma, the DMAIC method is used:

1. Define
2. Measure
3. Analyze
4. Improve
5. Control

Six Sigma is a "Problem focused" methodology, and the primary toolset of Six Sigma is Math and Statistics.

The Conflict Between Lean and Six Sigma
There is a "battle" within the Lean and Six Sigma professional communities among many who think their respective way is better and superior. In general, the Six Sigma side claims to be technically superior and that reducing variation gets to the root of the problem. The Lean side argues that basic flowcharting is more often than not all that is needed to produce high impact improvements.

This all has a "territorial" feel about it among consultants and aficionados of each approach or methodology. However, we know that tools are only a means to and end, and that we need to match the tool to the job. Such arguments and territorialism often arise when professionals are attached to the tool, and in essence are a "solution in search of a problem", and want to make sure their solution is chosen more often.

Does the Controversy Matter?
Tough times typically mean LEAN times, and these are tough time economically around the world. It seems that under those conditions, it would be more appropriate to focus on the challenge at hand and use the best tool(s) for the job. In my opinion, the controversy matters little.

Six Sigma and Lean go together hand in hand, although they often are differentiated. Despite any distinctions, the two go very well together and complement one another. For example, it could be a very logical approach to focus on Lean to achieve improved process flow, and at the same time develop a deeper understanding of the process. If more work is needed, Six Sigma could be used to reduce process variation. It seems very logical that they can be effectively deployed together.