Definitions for "Measurement error"
Measurement error occurs when we do not measure the true value for a unit, but instead measure the true value plus an error. Measurement error is unavoidable in surveys, but it can be reduced.
The difference between a measured value and a true value.
The difference between the observed value and the measurand.
The amount by which a measurement is incorrect because of problems inherent in the measuring process; also called bias.