U

U chart A control chart showing the count of defects per unit in a series of random samples.

UPPER CONTROL LIMIT A horizontal line on a control chart (usually dotted) which represents the upper limits of process capability.

Usability. (IEEE) The ease with which a user can operate, prepare inputs for, and interpret of a system or component.

User. (ANSI) Any person, organization, or functional unit that uses the services of an information processing system. See: end user.

User's guide. (ISO) Documentation that describes how to use a functional unit, and that may include description of the rights and responsibilities of the user, the owner, and the supplier of the unit. Syn: user manual, operator manual