The Six Sigma ‘Improve’ Phase



The “Improve” phase of a Six Sigma project identifies and implements the improvements to the process. This requires several activities:

Determine Possible Solutions

This three-step activity is similar to the Root Cause Analysis activity. Open with a brainstorming session to list all possible solutions. Narrow the list by eliminating the solutions which do not fully address the problem. Close this activity by documenting and planning the candidate solution(s).

There is always the possibility that the solution is blindingly obvious: something simple but overlooked. In that case, this activity is quick and painless.

On the other hand, it may become apparent that a combination of expensive or difficult steps is required to solve the problem.

Sometimes the lowliest team members, the department members or the “Yellow Belts”, can offer the clearest insights into the solutions.

A formal decision-making process would involve voting on a weighted set of criteria for each solution. Costs, time-lines, and effectiveness would be three criteria to consider. The “How to Choose a Six Sigma Project” article discussed this type of process in some detail. A Pugh matrix uses score values of +1, zero and -1 to indicate “better”, “equivalent”, or “worse” in each category; then that value is multiplied by the category’s weight; and the sum of weighted votes indicates the “best” solution(s).

One class of solution that is sometimes overlooked, but is very effective, is the poka yoke, or “error avoidance”, approach. This involves designing equipment or processes that prevent defects, or catch them before they go downstream. A familiar example is the USB connection: it cannot be inserted upside-down, so it prevents an operator from making an error. In manufacturing, a part might be placed into a jig immediately after an operation, to ensure it is the right size and shape; this catches defective work-in-process before it reaches the next process.

Implement the Candidate Solution(s)

This activity starts with planning the required changes. Time-lines, budgets, procurement and training may be involved to greater or lesser degrees. Certainly the Six Sigma team must communicate the type and scope of the changes being envisioned. Plan for the measurements required for the next stage.

The department’s leadership must be involved and committed to the solution(s). If they have experience in building up the department, they could make the implementation go relatively smoothly. If they have been caretakers rather than innovators, then the Six Sigma project team would have to carry more of the load.

Even the implementation process should be monitored. Delays or problems during implementation would have a negative effect on the cost/benefit and timeline of the overall project.

Evaluate the Effectiveness of the Solution(s)

Take measurements, much as were taken during the “Measure” phase.

Re-calculate the process sigma, particularly if this project’s goal was to reduce the defect rate.

The general rule, of course, is to compare the “before” and “after” pictures of the process. Has it improved? Has it improved to the expected degree?

Oskar Olofsson, 2011









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I am a Swedish-based Lean consultant, and the owner of the World-Class-Manufacturing.com web site.

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