6 sigma: A sample in which each sampling unit contains a pair of observations that are not independent of one another (e.g. sampling ages of husband and wife as a single sampling unit).

6 sigma: A type of hypothesis test used when analyzing the difference between the means obtained from paired samples.

TS 16949: Piece-to-piece variation due to measuring different parts.

MSA: It is the net effect of all significant and determinable sources of variation over time. Performances quantifies the long term assessment of combined measurement errors.