A tool for detecting variations in a process:

• A. Pie chart
• B. Bar chart
• C. Quality control chart
• D. T-chart

Answer: (C)

Monitoring a process for variations and stability is what a quality control chart is designed to do. It plots data over time with a central line (the average) and upper and lower control limits, so you can see whether the variation is just normal, random fluctuation or something unusual that requires investigation. When all points stay within the limits and patterns look random, the process is considered in control. If a point falls outside the limits or you notice a nonrandom pattern, that signals assignable-cause variation and prompts root-cause analysis and corrective action. This makes it the best tool for detecting variations in a process.

Pie charts show parts of a whole and don’t track how a process behaves over time. Bar charts compare categories at a single point in time, not how a process changes. A T-chart isn’t a standard tool for monitoring process stability over time. Quality control charts are specifically designed for this purpose, which is why they’re the right choice.