Response Bias

The response to a survey question is said to be biased if it does not reveal, on average, the true value of the target variable. This definition is closely related to the definition of a bias in statistics: The bias of an estimator is the difference between its expected value (when computed for a given sample) and the true value of the corresponding parameter (in the population). Biased responses may arise for many types of target variables: attitudes, behaviors, preferences, and expectations; sociodemographic characteristics such as age, level of education, or labor-market status; frequencies such as the number of purchases of a good or the number of doctor visits in a specified period; and monetary quantities such as income, financial assets, or consumption expenditure. This ...