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Crit Care. 2004 Feb;8(1):46-53. Epub 2003 Dec 30.

Statistics review 8: Qualitative data - tests of association.

Author information

1
Senior Lecturer, School of Computing, Mathematical and Information Sciences, University of Brighton, Brighton, UK. v.bewick@brighton.ac.uk

Abstract

This review introduces methods for investigating relationships between two qualitative (categorical) variables. The chi2 test of association is described, together with the modifications needed for small samples. The test for trend, in which at least one of the variables is ordinal, is also outlined. Risk measurement is discussed. The calculation of confidence intervals for proportions and differences between proportions are described. Situations in which samples are matched are considered.

PMID:
14975045
PMCID:
PMC420070
DOI:
10.1186/cc2428
[Indexed for MEDLINE]
Free PMC Article

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