Potential biases

Non-response in cross-sectional surveys can be a major problem. There are likely to be important differences between the people who respond to surveys and the people who do not respond and this may have an impact on the results of the study.

For example responders may be healthier or older and so subjects responding to a survey may not be representative of the subjects invited to take part in it and therefore it may not be possible to extrapolate the results to the population under review.