The primary purpose of a control chart is to...

The primary purpose of a control chart is to monitor a process over time for potential variation. Control charts are essential tools in quality control and Six Sigma methodologies, as they help visualize the performance of a process. By plotting data points over time, control charts enable practitioners to see how a process behaves and to identify if it remains stable or if it exhibits any variation that could indicate issues, such as special cause variation that may require investigation.

In practical applications, control charts can distinguish between common cause variation, which is inherent to the process, and special cause variation, which arises from specific factors outside the process's normal operation. By regularly monitoring these charts, teams can take proactive measures to improve process stability and quality.

While other options suggest relevant aspects of data analysis, they do not encapsulate the essential function of a control chart as effectively as the role of monitoring process variation. Identifying trends is a secondary function, showing distribution is more about data characterization rather than process control, and predicting future results falls outside the primary objective of establishing a baseline for process behavior. Thus, monitoring for potential variation directly addresses the control chart's fundamental purpose.