Six Sigma Green Belt Certification Practice Exam

When examining a process, which technique is used to minimize variation among similar items?

1. Activity network diagram

2. Confidence interval

3. Rational subgrouping

4. Affinity diagram

The correct answer is: Rational subgrouping

Rational subgrouping is the technique that focuses on minimizing variation among similar items by grouping data in a way that reflects the natural variation within a process. This approach entails organizing data into subgroups that are more homogenous, allowing for a more accurate comparison of performance and understanding of process behavior. By identifying common factors and controlling for variations, practitioners can identify trends and patterns that can lead to more consistent output and improved quality. In this process, the goal is to isolate specific sources of variation and reduce them, ideally leading to lower overall process variability. This method helps teams analyze data effectively, facilitating better decision-making based on accurate interpretations of the process performance. The other techniques mentioned, such as an activity network diagram, confidence interval, and affinity diagram, serve different purposes within process management and are not specifically aimed at minimizing variation among similar items. For instance, an activity network diagram is used for project scheduling, a confidence interval pertains to statistical estimation, and an affinity diagram assists in organizing ideas and data into groups based on natural relationships. These techniques do not focus directly on the variation aspect as rational subgrouping does.