Error-

• Nominal error - The quantitative difference between the nominal (or specified) and measured values of a measurand. See tolerance, geometric errors.
• Measurement error - The quantitative difference between the "true value" and measured value of a measurand. "True value" is inherently indeterminable but may be defined in practice. See uncertainty, accuracy.
• Statistical Error - Determined by repeated measurements of the same measureand. The multiple measurements are analyzed using statistical mathematics to determine such things as mean value and standard deviation. See also repeatability.