A control chart constructed using a range is known as what?

A control chart that utilizes the range of a set of data points to monitor process variability is known as an R-chart. The R-chart is specifically designed to track the range, which measures the difference between the maximum and minimum values within subgroups of data collected over time. This type of chart is valuable in quality control processes, as it helps identify variations in a manufacturing or service process that may indicate issues needing attention.

The R-chart is typically used in conjunction with the x̄ chart, which monitors the average of the data, to provide a comprehensive view of process stability. It helps to distinguish between common cause variation, which is inherent to the process, and special cause variation, which indicates an issue that should be addressed. Understanding the range through the R-chart is critical for maintaining consistent quality in production and minimizing defects.