The expected "overall" performance values quantitatively represent the actual process performance. The expected values are calculated using the overall sample variance.

·    PPM < LSL - expected number of parts per million that have measurements 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, 0.26 parts per million are expected to have measurements less than the LSL and 0.85 parts per million are expected to have measurements greater than the USL.