# Odds Ratio

From WikiLectures

This is defined as the ratio of odds of disease among exposed (odds_{1}) and odds of disease among unexposed (odds_{0}).

**OR = (odds**_{1}) / (odds_{0})

Disease | |||
---|---|---|---|

Yes | No | Total | |

Unexposed | A | B | A+B |

Exposed | C | D | C+D |

Total | A+C | B+D | N = A+B+C+D |

Using the above table, we can calculate the odds ratio using this formula:

**Risk difference percentage (RD%)** represents the proportion os cases in the exposed grip that were actually caused by the exposure. This is equal to *attributable fraction for exposed* (see below). It is calculate as follows:

**RD% = (r**_{1}− r_{0}) / r_{1}

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### Bibliography[✎ edit | edit source]

BENCKO, Vladimír. *Hygiene & Epidemiology : Selected Chapters. *2nd edition. Karolinum, 2011. Chapter 6.1: Principles of epidemiological studies. ISBN 978-80-246-0793-1.