What is the Risk Ratio?

Explanation

This can be said to be a ratio of the probabilities of risk in one group compared to the possibilities of an occurrence of risk in another group. It is commonly taken into use to present the outcomes of various groups. These are also termed relative risks.

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Risk Ratio Formula

The formula is as follows:

Or

Where,

  • CI = Cumulative Incidence,e = exposed group, andu = unexposed group,

  • e = experimental group (A group), andc = control group (B group).

How to Calculate the Risk Ratio?

  • From the above formula, it is clear that the calculation of risk ratio takes the incidence or risk of the event taking place in one group (experimental group) and draws a comparison with the incidence or risk of the event taking place in another group (control group).This is performed by examining two variables. One of the variables shall be used for measuring the incidence of an event (exposed vs. Unexposed), and the second variable shall be used for measuring both groups (Group A vs. Group B).It will then require the analyst to divide an exposed event for group A or the experimental group by the incidence of an unexposed event for group B or the control group. This is calculated by taking percentages into use.When the values equal 0, it means that not even a single case falling in group A had the incidence taking place, whereas the “x” number of case/s in group B had the incidence taking place. The values equal to 1 mean that the results are neutral. In other words, the probability of an event in one group shall be the same as the possibility of an event taking place in different groups.

Examples

Example #1

RR, in this case, can be determined by using the formula –

  • R.R = CIe / CIu= 6.02% / 2.47%

  • R.R. = 2.436

Example #2

  • R.R = CIe / CIu= 6.67% / 3.61%

  • R.R. = 1.844

Interpretation

  • This is as important as the calculation of the same. The results of the risk ratio can be equal to zero or one or greater or lower than 1. When the results are more significant than zero, it signifies that none of the incidences in the experimental group or group A had the probability of the event taking place, whereas ‘x’ no. of incidences in the control group or group B had the likelihood of the event taking place.When the results are equal to one, then it is regarded as neutral, or in other words, the incidences in an experimental group are the same as the incidences in a control group.When the result is more significant than one, it means that the risk in the exposed group is greater than in the unexposed group. Similarly, when the result is lower than one, it signifies that the risk in the exposed group is lower than in the unexposed group.

Conclusion

These methods are commonly taken into use for drawing useful comparisons between two groups. The comparisons between the two groups are performed based on the likelihood or probability of an event that can take place in these groups. This is also regarded as a relative risk.

One of the two groups is regarded as an experimental group, whereas the other is the control group. It should not be deemed an inferential statisticInferential StatisticInferential statistics helps study a sample of data and make conclusions about its population. read more since it is a descriptive statistic and does not evaluate a particular statistic’s significance.

This can be determined using the formula stated below:

A risk ratio equal to one means that the outcomes of both groups are identical. On the other hand, a higher or lower rate would indicate the underlying factor responsible for increasing or decreasing the risks in either or both groups.

This has been a guide to What is the Risk Ratio & its definition. Here we discuss the formula to calculate risk ratio and interpretation along with examples. You can learn more about it from the following articles –

  • Calculate Risk-Reward RatioWhat are Operational Risks?Loss RatioRisk-Weighted Asset FormulaRelative Risk Reduction Formula