The Improve Phase of a Lean Six Sigma Project
Improve phase is the fourth phase of Lean Six Sigma projects. Following are the deliverable of this phase:
Identify Solutions to overcome the impact of root causes
For each of the root causes identified in the Analyze phase, the Lean Six Sigma Team uses an apt structured or unstructured brainstorming method to generate various alternatives to overcome the problem.
These techniques may include Channeling, Anti-solutions, Analogy, Wishful thinking, Random word stimulus methods, etc.
SCAMPER is another popular method which can be used by the Six Sigma Green Belt to systematically improve the current process using any of the following methods: Simplify or Substitute, Combine, Adapt, Modify, Put to different use, Eliminate & Reduce.
If there are too many options that the team has identified, then a variety of solution screening methods can be used to select the best solution for implementation. These screening methods include NGT (Nominal Group Technique), N/3 Voting, Criteria Based Matrix (CBT), etc.
Proposed solutions can be a new process, technology change, policy changes, alterations of inputs, measurement system refinement, customer, employee or vendor education, etc. In such cases, either revised process map, future state value stream mapping, etc., may need to be proceeded.
The solution that the team has selected should directly impact the CTQ of the project. Six Sigma Green Belt should validate this.
Refining the Solutions (FMEA, Poka-Yoke)
Before implementing solutions, the Six Sigma Green Belt needs to ensure that the proposed solutions are complete and well refined. This will ensure that there are no delays, rework during implementation, and the full impact on CTQ is derived.
In order to do this, a tool called Failure Modes Effect Analysis (FMEA) is used. The main purpose of this tool is to assess all the risks involved with a solution, and how to mitigate them by refining the solution before implementation.
Risk Priority Number (RPN) derived from FMEA helps in prioritizing the risks and acting on them in a systematic manner.
Mistake-proofing (Poka-Yoke, in Japanese) is a method used to ensure that the proposed solution doesn’t create additional defects or errors. This can be used in conjunction with FMEA.
Now the solution is ready for pilot. The purpose of the pilot is to assess its impact in a control group setting. Based on the qualitative and quantitative results of the pilot, necessary alternations can be incorporated to the final solution.
A Six Sigma Green Belt should closely work with the process owners during pilot to understand ground realities and build ownership.
Statistically validate results
In Lean Six Sigma Projects, it is an important step to statistically validate the impact on CTQ (before implementation & after Implementation).
Hypothesis tests like 2-t test, ANOVA, Chi-square tests, etc., are used to perform this statistical validation.
These tests help to identify if the improvement is significant or marginal in nature.
Six Sigma Green Belt should be able to select and perform appropriate tests using statistical software.
On successful completion of these deliverable and formal Improve tollgate review, the Lean Six Sigma project team is ready to move to the Control phase.
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