The Capability Plot is located in the lower center of the Capability Sixpack - Normal.

The capability plot consists of three intervals:

·    The within interval represents the potential process tolerance and is calculated by six times the within-subgroup 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) that you specified.

Compare the within and overall intervals to the specifications interval. If the within and overall intervals are contained within the specification intervals, then you can conclude that the process is producing units that conform to specifications.

For the piston data, the within and overall intervals are contained well within the specification interval, implying that at least 99.74% of the measurements are within the specification interval.