Non-response bias refers to the mistake one expects to make in estimating a population characteristic based on a sample of survey data in which, due to non-response, certain types of survey respondents are under-represented. Social scientists often attempt to make inferences about a population by drawing a random sample and studying relationships among the measurements contained in the sample. When individuals from a special subset of the population are systematically omitted from a particular sample, however, the sample cannot be said to be “random,” in the sense that every member of the population is equally likely to be included in the sample. It is important to acknowledge that any patterns uncovered in analyzing a non-random sample do not provide valid grounds for generalizing about a population in the same way that patterns present in a random sample do. The mismatch between the average characteristics of respondents in a non-random sample and the average characteristics of the population can lead to serious problems in understanding the causes of social phenomena and may lead to misdirected policy action. Therefore, considerable attention has been given to the problem of non-response bias, both at the stages of data collection and data analysis.
