title: Sampling in epidemiological research: issues, hazards and pitfalls.
abstract: Surveys of people's opinions are fraught with difficulties. It is easier to obtain information from those who respond to text messages or to emails than to attempt to obtain a representative sample. Samples of the population that are selected non-randomly in this way are termed convenience samples as they are easy to recruit. This introduces a sampling bias. Such non-probability samples have merit in many situations, but an epidemiological enquiry is of little value unless a random sample is obtained. If a sufficient number of those selected actually complete a survey, the results are likely to be representative of the population. This editorial describes probability and non-probability sampling methods and illustrates the difficulties and suggested solutions in performing accurate epidemiological research.
authors.affiliation: Newcastle University, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Tyrer
authors.affiliation: University of Huddersfield, UK.
authors.forename: Bob
authors.initials: B
authors.lastname: Heyman