DMAIC Analyze Phase
The A in DMAIC is about finding the top 1-3 causes of the problem we are attacking. When well executed, this phase starts with team input regarding potential causes and uses statistical methods to isolate the top 1 to 3 causes. Oftentimes there is one primary cause that is driving most of the unwanted variation, and controlling or eliminating this cause is all that is needed.
Explore potential causes – listen to the team
Recruiting internal (and sometimes external) experts who are most familiar with the product and/or process will drastically improve the team’s likelihood of a successful outcome. Team members that work with the process on a daily basis can be extremely valuable as well.
There are a number of methods for exploring potential causes, including fishbone diagrams for organizing potential variation sources and 5-Why sessions for mapping top-level symptoms to underlying root causes. Team members can collect data between team meetings and help build Pareto charts and gain insight into potential causes using dot plots.
Isolate top causes
This is the most important, and often the most challenging step in a Six Sigma project. While the first half of the Analyze phase focuses on gathering team input, the second half must focus on eliminating the “trivial many” causes and identifying the “vital few.” There are a number of tools to help accomplish this task.
In manufacturing environments, we’ve found the Shainin Methods to be extremely powerful in quickly isolating the vital few causes, without interrupting production. Techniques such as Paired Comparisons, Multi-Vari, and Components Search are among the most powerful that we have used.
We highly recommend Keki Bhote’s book, World Class Quality, which details the use of these tools. Keki is a Motorola veteran who has solved some incredibly challenging problems in his time, and he is also a very motivating writer. Also, the Shainin Group is one of the best consulting teams for manufacturing problem-solving anywhere. If you are a manufacturer with a sizable training budget, give them some serious consideration.
The analyze phase cannot conclude until the top causes have been confirmed. Among the most useful tools we’ve seen in this area are the Shainin Methods, hypothesis testing, and basic design of experiments (DOE).
Preventing future problems with PFMEA
Effective Six Sigma teams go beyond understanding the current causes of unwanted variation, and dedicate time to anticipating and controlling other risks that could adversely affect the process in the future (this is the difference between corrective action and preventive action!).
Conducting a Process Failure Modes and Effects Analysis (PFMEA) is a best-practice method for assessing all process risks associated with one or more CTQ’s. PFMEA’s can be conducted on an entire process (which is typically the case with new product launches) or a collection of process steps that affect a CTQ of interest.