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How do you convert odds ratio to risk ratio?
To convert an odds ratio to a risk ratio, you can use “RR = OR / (1 – p + (p x OR)), where p is the risk in the control group” (source: http://www.r-bloggers.com/how-to-convert-odds-ratios-to-relative-risks/).
Is risk ratio the same as odds ratio?
The relative risk (also known as risk ratio [RR]) is the ratio of risk of an event in one group (e.g., exposed group) versus the risk of the event in the other group (e.g., nonexposed group). The odds ratio (OR) is the ratio of odds of an event in one group versus the odds of the event in the other group.
Can you calculate risk from odds?
The simplest way to ensure that the interpretation is correct is to first convert the odds into a risk. For example, when the odds are 1:10, or 0.1, one person will have the event for every 10 who do not, and, using the formula, the risk of the event is 0.1/(1+0.1) = 0.091.
How do you calculate confidence interval for risk ratio?
To calculate a 95% confidence interval for the risk ratio parameter, convert the risk ratio estimate to a natural log (ln) scale. (Use the ln key or “inverse e” key on your calculator.) For the illustrative data, the natural log of the risk ratio = ln(4.99) = 1.607.
How do I calculate odds ratio?
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.
How to convert odds ratio to risk ratio?
To understand what an odds ratio means in terms of changes in numbers of events it is simplest to first convert it into a risk ratio, and then interpret the risk ratio in the context of a typical control group risk, as outlined above. The formula for converting an odds ratio to a risk ratio is provided in Chapter 12 (Section 12.5.4.4 ).
What does a value of 1 mean for the risk ratio?
For both measures a value of 1 indicates that the estimated effects are the same for both interventions. Neither the risk ratio nor the odds ratio can be calculated for a study if there are no events in the control group.
How to calculate the 95% confidence interval for the odds ratio?
The formula for the 95% Confidence Interval for the odds ratio is as follows: The standard error for log (OR) is computed using the following equation: We will illustrate computation of a 95% confidence interval for the data in the contingency table shown above.
When to use odds ratio in a study?
Note that while we have discussed using the odds ratio as a measure of association in the context of a case-control study, odds ratios can also be computed in other types of study designs as well. Recall our example of a prospective cohort study to examine the association of hypertension and cardiovascular disease.