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Glossary “N” Definition of Terms in DataMyte


For a product whose size is of concern: the desired mean value for the particular dimension — the target value. 

Nominal Chart

A control chart that plots the deviation from the nominal value. Often used when individual samples are taken in short-run, low-volume processes. Allows multiple part numbers manufactured by similar processes to be plotted on the same control charts.

Nonconforming Unit

A sample (part) that has one or more nonconformities, making the sample unacceptable for its intended use. See also Defective Unit. 


A departure of a quality characteristic from its intended level or state. See also Defect.

Nonlinearity (of a measuring instrument)

The deviation of the instrument’s response from linearity. 

Normal Distribution

A probability distribution given mathematically by the formula. The normal distribution is a good approximation for a large class of situations. One example is the distribution resulting from the random additions of a large number of small variations. The Central Limit Theorem expresses this for the distribution of means of samples; the distribution of means results from the random additions of a large number of individual measurements, each of which contributes a small variation of its own.

Normal Distribution Formula


For attribute data: a control chart of the number of defective units in a subgroup. Assumes a constant subgroup size.

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