Six Sigma Green Belt Certification Practice Exam

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

1. Confidence interval

2. Activity network diagram

3. Rational subgrouping

4. Affinity diagram

The correct answer is: Rational subgrouping

The correct answer is rational subgrouping, which is a technique used to minimize variation among similar items in a process. Rational subgrouping involves dividing a larger group of data into smaller, more homogenous groups or subgroups. By analyzing these smaller subgroups, practitioners can identify and understand variations that occur within the process. This method helps ensure that the data collected reflects the process' natural variation and prevents the masking of important differences within the data set. Using rational subgrouping effectively facilitates better decision-making and insights into process improvements. It allows teams to focus on controlling variations that are inherent to the process and to identify any trends or special causes of variation that may need to be addressed. The other methods mentioned—confidence intervals, activity network diagrams, and affinity diagrams—serve different purposes. For instance, confidence intervals are used for estimating population parameters and understanding the precision of sample statistics, while activity network diagrams help in scheduling and visualizing tasks in a project. Affinity diagrams are useful for organizing ideas and identifying relationships among concepts, but they do not specifically target minimizing variation in processes. Thus, focusing on rational subgrouping is the most appropriate choice in the context of reducing variation among similar items.