The capability plot is located at the lower right corner of the Between/Within Capability Sixpack Report.
The capability plot consists of three intervals:
- The between/within interval represents the potential process tolerance and is calculated by six times the B/W (between and within) standard deviation.
- The overall interval represents the actual process tolerance and is calculated by six times the overall standard deviation.
- The specification interval represents the interval between the lower and upper specification limits (LSL and USL.
The process center is shown by the tick mark inside the Overall and B/W process spread intervals. The target, if you have one, is shown by the tick mark inside the specification spread (Specs).
Use the capability plot to visually assess the capability of your process.
Compare the B/W and overall intervals to the specification interval. For a capable process, the B/W and overall intervals should be narrower than the specification interval and centered at the target or center of the specifications.
Compare the process center to the target, if you have one. If the process is centered (on target), the middle tick marks for the specifications and for the process spread are vertically aligned. If the process is not centered, investigate the reasons why.