Potential Root Causes
In many cases, clues to the factors affecting performance are already available based on the work that was done in Define and Measure. Perhaps the team demonstrated that the problem is isolated to one group, and they know that group is using older equipment. Or analysis of the process map may have revealed some fairly obvious sources of inefficiency and delay in the process.
However, this is not sufficient to confirm what is causing the problem for two reasons. One is that, as in all phases of DMAIC, suspicions and hypotheses must be confirmed with data. Not only must the team confirm that these factors are present, they must also confirm that changes in these factors substantially impact the outcome. The other is that the goal of Analyze is to determine root causes, which requires digging deeper than what is apparent on the surface.
Several techniques are employed by Six Sigma project teams to identify potential root causes. One is brainstorming, which is used by team members and, ideally, people involved in performing the process under study, to create a large list of factors which could reasonably affect performance. This list will of course include any factors that were revealed based on the process mapping exercise and the data analysis conducted during Measure.
Another popular exercise is the 5 Whys, which involves repeatedly asking “Why?" until it no longer makes sense to do so. The point is to get past the surface-level answers that are likely to be put forth initially, and to uncover the real underlying issues.