Chambers, R., Measurement Error in Auxiliary Information, Centre for Statistical and Survey Methodology, University of Wollongong, Working Paper 08-08, 2008, 18p.
Survey data are not just the data collected from the responding sample. There are typically many other sources of information about the characteristics of the sampled population that can be used to improve inference. The data contained in these sources is often referred to as auxiliary data in the survey sampling literature. Inference using the survey data that exactly recovers key population characteristics associated with this auxiliary information is said to be calibrated on these characteristics, and is typically viewed as superior to inference that does not necessarily achieve this outcome.