Contents
When can you use odds ratio?
Odds ratios frequently are used to present strength of association between risk factors and outcomes in the clinical literature. Odds and odds ratios are related to the probability of a binary outcome (an outcome that is either present or absent, such as mortality).
How are odds ratios calculated?
The odds ratio is calculated by dividing the odds of the first group by the odds in the second group. In the case of the worked example, it is the ratio of the odds of lung cancer in smokers divided by the odds of lung cancer in non-smokers: (647/622)/(2/27)=14.04.
When should odds ratio not be used?
Unfortunately, there is a recognised problem that odds ratios do not approximate well to the relative risk when the initial risk (that is, the prevalence of the outcome of interest) is high. Thus there is a danger that if odds ratios are interpreted as though they were relative risks then they may mislead.
Is odds ratio a measure of risk?
Odds ratios (OR) are commonly reported in the medical literature as the measure of association between exposure and outcome. However, it is relative risk that people more intuitively understand as a measure of association. Relative risk can be directly determined in a cohort study by calculating a risk ratio (RR).
Why is the odds ratio an indirect measure of risk?
Called an indirect measure of risk because incidence rates have not been used; instead, the risk of an outcome associated with an exposure is estimated by calculating the odds of exposure among the cases and controls. -When OR=1, there is no association between exposure and outcome.
Is a rate the same as a ratio?
A ratio is a comparison of two numbers. A rate , by contrast, is a comparison of two quantities which can have different units. For example 5 miles per 3 hours is a rate, as is 34 dollars per square foot.
How do you calculate the cumulative odds ratio?
Using standard statistical software, for each subject we create a separate record for each response threshold and then apply binary logistic regression to estimate generalized cumulative odds ratios for one or more exposures.
How is the odds ratio in a case control study calculated?
The odds ratio is calculated using the number of case -patients who did or did not have exposure to a factor (such as a particular food) and the number of controls who did or did no t have the exposure. The odds ratio tells us how much higher the odds of exposure are among case-patients than among controls.
What is the odds ratio for maximum likelihood?
The cumulative odds ratio obtained by maximum likelihood is 3.0 [95% confidence interval (CI), 2.5, 3.7]. As can be seen in Table 3, the person-threshold cumulative odds ratio is 3.5 (95% CI, 2.8, 4.3).
How is the odds ratio used in economics?
The odds ratio can also be used to determine whether a particular exposure is a risk factor for a particular outcome, and to compare the magnitude of various risk factors for that outcome. OR=1 Exposure does not affect odds of outcome. OR>1 Exposure associated with higher odds of outcome. OR<1 Exposure associated with lower odds of outcome.