<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (September 2016) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (September 2016) (Learn how and when to remove this template message) </Td> </Tr> <P> Observational error (or measurement error) is the difference between a measured value of a quantity and its true value . In statistics, an error is not a "mistake ." Variability is an inherent part of the results of measurements and of the measurement process . </P> <P> Measurement errors can be divided into two components: random error and systematic error . </P>

What are the sources of error in measurement