Xbar chart
The Xbar chart compares the subject-to-subject variation to the repeatability component. The Xbar chart consists of:
Plotted points, which represent, for each technician, the average measurements of each head.
Center line, which is the overall average for all head measurements by all technicians.
Control limits (UCL and LCL), which are based on the number of measurements in each average and the repeatability estimate.