Six Sigma Green Belt Certification Practice Exam

What is the mechanism by which the capability of a process is identified?

1. Creating rational subgroups

2. Performing process mapping

3. Performing rational sampling

4. Creating flow charts

The correct answer is: Creating rational subgroups

The identification of a process’s capability is fundamentally linked to the statistical methods used to analyze its performance, which is effectively achieved through creating rational subgroups. This method involves collecting data in a way that allows for a clear assessment of variability within a process. By grouping data into rational subgroups—where samples are taken under consistent conditions and variations are minimized—one can obtain a better representation of the process's consistency and performance over time. Using rational subgroups allows for the calculation of control limits and process capability indices, such as Cp and Cpk, which are essential metrics in Six Sigma methodologies. These metrics help in determining how well a process is performing relative to its specifications and how capable it is of producing products within those specifications consistently. While the other techniques like process mapping, rational sampling, and creating flow charts serve important roles in understanding and analyzing processes, they don't specifically target the statistical evaluation of capability in the same way that rational subgroups do. Process mapping can identify inefficiencies, rational sampling helps in understanding sampling methods, and flow charts offer a visual representation of the process but do not directly measure process capability.