Certified Production & Operations Manager (POM) Practice Exam

In quality control, which chart is specifically designed to monitor the number of defects?

1. p-chart

2. c-chart

3. x-bar chart

4. R-chart

The correct answer is: c-chart

The c-chart is specifically designed to monitor the number of defects in a sample or process over time. This chart is particularly useful for countable data where the number of defects can vary, but where the area of opportunity remains constant. It helps in determining whether the process is in control concerning the number of defects produced. When using a c-chart, the focus is on the actual count of defects rather than the proportion or percentage, which is what a p-chart would monitor. The c-chart assists in identifying trends, shifts, or any patterns that may indicate whether the processes are stable or if changes need to be made to reduce the occurrence of defects. In contrast, the other charts serve different purposes; the x-bar chart monitors the average of a measurable characteristic in a process, and the R-chart tracks the range of variability in the process data, neither of which focus on the count of defects. Therefore, the c-chart is the appropriate choice for monitoring the number of defects in quality control.