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**N**

**n:** The number of units in a sample.

**N:** The number of units in a population.

**National Institute of Standards and Technology (NIST):** An agency of the U.S. Department of Commerce that develops and promotes measurements, standards and technology. NIST manages the Malcolm Baldrige National Quality Award.

**Natural team:** A team of individuals drawn from a single work group; similar to a process improvement team except that it is not cross functional in composition and it is usually permanent.

**Next operation as customer:** The concept of internal customers in which every operation is both a receiver and a provider.

**Noise:** Inputs that cause random and expected process variation. Noise factors are usually the unknown source of variation and are not controlled.

**Nominal group technique:** A technique, similar to brainstorming, used by teams to generate ideas on a particular subject. Team members are asked to silently come up with as many ideas as possible, writing them down. Each member is then asked to share one idea, which is recorded. After all the ideas are recorded, they are discussed and prioritized by the group.

**Nonconformity:** The nonfulfillment of a specified requirement (see also "blemish," "defect" and "imperfection").

**Nondestructive testing and evaluation (NDT, NDE):** Testing and evaluation methods that do not damage or destroy the product being tested.

**Nonlinear parameter estimation:** A methodology whereby the arduous, labor-intensive and distinctly frustrating task of multiparameter model calibration can be carried out automatically under the control of a computer.

**Nonparametric tests:** Nonparametric tests are often used in place of their parametric counterparts when certain assumptions about the underlying population are questionable. For example, when comparing two independent samples, the Wilcoxon Mann-Whitney test (see listing) does not assume the difference between the samples is normally distributed, whereas its parametric counterpart, the two-sample t-test, does. Nonparametric tests may be, and often are, more powerful in detecting population differences when certain assumptions are not satisfied. All tests involving ranked data (data that can be put in order) are nonparametric.

**Nonvalue added:** A term that describes a process step or function that is not required for the direct achievement of process output. This step or function is identified and examined for potential elimination.

**Norm (behavioral):** Expectations of how a person or persons will behave in a given situation based on established protocols, rules of conduct or accepted social practices.

**Normal distribution (statistical):** The charting of a data set in which most of the data points are concentrated around the average (mean), thus forming a bell shaped curve.

**Normality:** A normality test is a statistical process used to determine if a sample or any group of data fits a standard normal distribution. A normality test can be performed mathematically or graphically.

**np chart:** A chart used to monitor the number of items defective for a fixed sample size.

**Number of affected units chart:** A control chart for evaluating the stability of a process in terms of the total number of units in a sample in which an event of a given classification occurs.