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Statistics review 11: Assessing risk

Viv Bewick1*, Liz Cheek1 and Jonathan Ball2

Author Affiliations

1 Senior Lecturer, School of Computing, Mathematical and Information Sciences, University of Brighton, Brighton, UK

2 Senior Registrar in ICU, Liverpool Hospital, Sydney, Australia

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Critical Care 2004, 8:287-291 doi:10.1186/cc2908

Published: 30 June 2004

Abstract

Relative risk and odds ratio have been introduced in earlier reviews (see Statistics reviews 3, 6 and 8). This review describes the calculation and interpretation of their confidence intervals. The different circumstances in which the use of either the relative risk or odds ratio is appropriate and their relative merits are discussed. A method of measuring the impact of exposure to a risk factor is introduced. Measures of the success of a treatment using data from clinical trials are also considered.

Keywords:
absolute risk reduction; attributable risk; case-control study; clinical trial; cross-sectional study; cohort study; incidence; number needed to harm; number needed to treat; odds ratio; prevalence; rate ratio; relative risk (risk ratio)