What type of chart is used to monitor process variability over time?

The X-bar and R chart is specifically designed to monitor process variability over time. It is commonly used in statistical quality control to observe changes in the mean and range of a process, helping to determine whether the process remains stable or if it exhibits signs of variability that could indicate issues.

The X-bar chart tracks the average values of samples taken from a process, while the R chart monitors the range of variation within those samples. Together, they provide insight into both the central tendency and the dispersion of the process data. By analyzing these charts over time, operators can identify trends, detect shifts in the process, and take corrective actions when necessary.

In contrast, a Pareto chart focuses on identifying the most significant factors in a dataset, a scatter plot is useful for assessing relationships between two variables, and a histogram provides a visual representation of frequency distribution but does not specifically monitor variability over time. These charts serve their unique purposes but do not provide the same real-time monitoring capabilities for process variability as the X-bar and R chart.