CPIM Practice Exam

What do control charts primarily record?

1. Average of specification limits over time

2. Root causes of process variation

3. Range of each set of samples taken over time

4. Mean of the results from product inspection

The correct answer is: Range of each set of samples taken over time

Control charts are essential tools in quality management and process control that help visualize how a process behaves over time. Their primary function is to graphically represent data collected at various points in a process to monitor its stability and performance. The selection of the range of each set of samples taken over time is correct because control charts typically plot individual data points, as well as the average and range, to observe variations. This allows practitioners to identify trends, shifts, or any inconsistencies within the process that may need correction. By focusing on the range, control charts can effectively illustrate the dispersion of data, enabling organizations to maintain quality standards by monitoring performance metrics and making data-driven decisions. While other options may touch upon relevant aspects of process management or quality control, they do not accurately capture the primary function of control charts as framed by the way options were structured. For instance, the average of specification limits looks at quality targets rather than process performance, root causes of variation deal more with analysis rather than real-time monitoring, and means from product inspections may inform results but don’t focus on ongoing process control. Hence, option C stands out as it directly correlates with the designated purpose of control charts in tracking the variability within a process over time.