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Non-response is a significant problem for survey research, due to the potential bias in the findings that can result when those sampled do not take part. Non-response to the survey occurs where eligible households refuse to take part (ie refusals) or where the members of eligible households could not be contacted during the survey assignment (ie non-contacts).
Bias will result should the characteristics of those who take part in the survey differ greatly from those who do not take part. It is therefore important to attempt to discover the characteristics of those who do not take part.