What is applicable for control charts?

Control charts are a vital tool in quality control and process management, primarily used to monitor the stability of processes over time. Option B is correct because control charts are designed to identify variations in processes. When data points fall outside the control limits, this indicates that the process may be experiencing special cause variation rather than common cause variation, warranting further investigation. This helps organizations understand if an intervention is needed to bring the process back into a state of control.

The other options do not accurately reflect the characteristics of control charts. For instance, control charts do not focus solely on average values; they consider both the average and the variation in the data. They can also be applied to historical data to assess trends and changes over time. Finally, the assertion that control charts always generate a straight line is misleading; while they often display control limits as horizontal lines, the data points may vary significantly and may not form a straight line. This variability is essential for interpreting the stability of the process being monitored.