An X-bar is a control chart used with processes that have a subgroup size of two or more. X - bar chart helps us to determine if a process is stable and predictable.It shows how the mean or average changes over time.
T o determine the A2 factor for the X-bar chart of a particular sample size, n, check the table of control chart constant.
For a sample size of 12, the A2 constant for the X-bar chart is 0.266
