The expected "within" performance values quantitatively represent the potential process performance if the process did not have the shifts and drifts between subgroups. The expected values are calculated using the within-subgroup variation.

·    PPM < LSL - expected number of parts per million that have measurements less than the lower specification limit. PPM < LSL equals 1,000,000 times the chance that the measurement of a randomly-selected part from the within-subgroup distribution is less than the lower specification limit.

·    PPM > USL - expected number of parts per million that have measurements greater than the upper specification limit.

·    PPM Total - expected number of parts per million that have measurements located beyond the specification interval. It is the total of PPM < LSL and PPM > USL.

For the piston data, 0.18 parts per million are expected to have measurements less than the LSL and 0.59 parts per million are expected to have measurements greater than the USL.