What is the difference between odds ratio and risk difference?

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.

Are odds ratio and risk ratio similar?

The relative risk (RR), also sometimes known as the risk ratio, compares the risk of exposed and unexposed subjects, while the odds ratio (OR) compares odds. A relative risk or odds ratio greater than one indicates an exposure to be harmful, while a value less than one indicates a protective effect.

Is it important to distinguish between a risk ratio and an odds ratio?

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).

Is risk and rate ratio the same?

Rate ratios are closely related to risk ratios, but they are computed as the ratio of the incidence rate in an exposed group divided by the incidence rate in an unexposed (or less exposed) comparison group.

What is the difference between odds and ratio?

Odds are the probability of an event occurring divided by the probability of the event not occurring. An odds ratio is the odds of the event in one group, for example, those exposed to a drug, divided by the odds in another group not exposed.

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 odds ratio larger than risk ratio?

The figures show that the odds ratio will always exaggerate the size of the effect compared with a relative risk. That is, if the odds ratio is less than one then it is always smaller than the relative risk. Conversely, if the odds ratio is greater than one then it is always bigger than the relative risk.

Why is odds ratio bigger than risk ratio?

The discrepancy between the odds ratio and the relative risk becomes large only when there are large effects (a twofold or threefold increase in risk) for groups already at a large initial risk.

How do you explain risk differences?

The risk difference is calculated by subtracting the cumulative incidence in the unexposed group (or least exposed group) from the cumulative incidence in the group with the exposure.

How do you convert odds to risks?

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.