Odds ratio: Difference between revisions
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The '''odds ratio''' is a technical term often used in medical statistics. The odds ratio is the ratio of the relative incidence of a target disorder in the experimental group relative to the relative incidence in a control group. Essentially, it reflects how the risk of having a particular disorder is influenced by the treatment. An odds ratio of 1 means that there is no benefit of treatment compared to the control group.<ref name="urlOdds and odds ratio">{{cite web |url=http://www.jr2.ox.ac.uk/bandolier/booth/glossary/Odds.html |title=Odds and odds ratio |author=Anonymous |authorlink= |coauthors= |date= |format= |work= |publisher=Bandolier |pages= |language= |archiveurl= |archivedate= |quote= |accessdate=}}</ref> | The '''odds ratio''' is a technical term often used in medical statistics. The odds ratio is the ratio of the relative incidence of a target disorder in the experimental group relative to the relative incidence in a control group. Essentially, it reflects how the risk of having a particular disorder is influenced by the treatment. An odds ratio of 1 means that there is no benefit of treatment compared to the control group.<ref name="urlOdds and odds ratio">{{cite web |url=http://www.jr2.ox.ac.uk/bandolier/booth/glossary/Odds.html |title=Odds and odds ratio |author=Anonymous |authorlink= |coauthors= |date= |format= |work= |publisher=Bandolier |pages= |language= |archiveurl= |archivedate= |quote= |accessdate=}}</ref> | ||
The odds ratio is a difficult concept and recommendations for | The odds ratio is a difficult concept and recommendations for how to teach its use are available.<ref name="pmid18181004">{{cite journal |author=Prasad K, Jaeschke R, Wyer P, Keitz S, Guyatt G |title=Tips for teachers of evidence-based medicine: understanding odds ratios and their relationship to risk ratios |journal=J Gen Intern Med |volume=23 |issue=5 |pages=635–40 |year=2008 |month=May |pmid=18181004 |doi=10.1007/s11606-007-0453-4 |url=http://dx.doi.org/10.1007/s11606-007-0453-4 |issn=}}</ref> | ||
==Example== | |||
This example is from the Titanic (example from Power<ref name="pmid">{{cite journal |author=Power M |title=Resource reviews |journal=Evidence-based Medicine |volume=13 |issue=3 |pages=92 |year=2008 |pmid=18515638 |doi= |url=http://ebm.bmj.com/cgi/content/full/13/3/92 |issn=}}</ref>): | |||
'''Male passengers''':<br> | |||
142 survived, 709 died | |||
* Odds of survival = 142/709 = 0.20 | |||
* Probability (risk or chance) of survival = 142/(142+709) = 17% | |||
'''Female passengers''':<br> | |||
308 survived, 154 died | |||
* Odds of survival = 308/154 = 2.00 | |||
* Probability (risk or chance) of survival = 308/(308+154) = 67% | |||
'''Comparison''': | |||
* Odds ratio (OR) for survival = 0.20/2.00 = 0.10 | |||
* Relative risk (RR) for survival = 17%/67% = 0.25 | |||
==References== | ==References== | ||
Revision as of 10:51, 2 June 2008
The odds ratio is a technical term often used in medical statistics. The odds ratio is the ratio of the relative incidence of a target disorder in the experimental group relative to the relative incidence in a control group. Essentially, it reflects how the risk of having a particular disorder is influenced by the treatment. An odds ratio of 1 means that there is no benefit of treatment compared to the control group.[1]
The odds ratio is a difficult concept and recommendations for how to teach its use are available.[2]
Example
This example is from the Titanic (example from Power[3]):
Male passengers:
142 survived, 709 died
- Odds of survival = 142/709 = 0.20
- Probability (risk or chance) of survival = 142/(142+709) = 17%
Female passengers:
308 survived, 154 died
- Odds of survival = 308/154 = 2.00
- Probability (risk or chance) of survival = 308/(308+154) = 67%
Comparison:
- Odds ratio (OR) for survival = 0.20/2.00 = 0.10
- Relative risk (RR) for survival = 17%/67% = 0.25
References
- ↑ Anonymous. Odds and odds ratio. Bandolier.
- ↑ Prasad K, Jaeschke R, Wyer P, Keitz S, Guyatt G (May 2008). "Tips for teachers of evidence-based medicine: understanding odds ratios and their relationship to risk ratios". J Gen Intern Med 23 (5): 635–40. DOI:10.1007/s11606-007-0453-4. PMID 18181004. Research Blogging.
- ↑ Power M (2008). "Resource reviews". Evidence-based Medicine 13 (3): 92. PMID 18515638. [e]