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Selection of subjects for study 

Selection of subjects for study
Selection of subjects for study

Mark Elwood

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date: 19 April 2021

This chapter discussed principles of subject selection and defines target, source, eligible, entrant and participant populations. Selection issues and selection bias may affect internal validity, external validity, and modify the hypothesis being tested. It shows methods to reduce selection biases and to define participation rate and response rate. Principles for the selection of the exposed or test group and the comparison groups are shown for all studies. In randomised trials, intention-to-treat analysis, contamination, blinding, data monitoring, stopping rules, the CONSORT format, and trial registration are discussed. For observational studies, it shows the purpose of control groups, issues of definition and choice of controls, institutional and community controls, and frequency and individual matching. Many examples are given.

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