The chart consists of the following:

·    The plotted points, which represent, for each operator, the average measurement on each part.

·    The green center line, which is the overall average for all part measurements by all operators.

·    The red control limits (UCL and LCL), which are based on the repeatability estimate and the number of measurements in each average.

Because the parts chosen for a Gage R&R study should represent the entire range of possible parts, this graph should ideally show lack-of-control. Lack-of-control exists when many points are above the upper control limit and/or below the lower control limit.

For the refraction data, few points are beyond the control limits for each operator. This indicates that the measuring system is inadequate.