 # Calculating The Hazard Ratios

The hazard ratio is a trickier calculation. To do it with complete perfection, first you need to understand what it actually is. The hazard ratio is mostly used in survival analysis and its most popular use is drug studies. It is the difference between the ratios of the hazard rates of the hazard between two groups. The values can either be corresponding or parallel. It depicts the differences between two survival curves using all the time slices. When the mention of time slices comes up, people often confuse it with risk ratio. The hazard ratio is different from the risk ratio as the risk ratio is only spread over one time slice. The hazard ratio, however, tells the difference using all time slices.

The Average Hazard Ratio

In most calculations, the interest is more focused on the comparison between the concerned times to event rate. As the calculation is not simple, it is done using a formula in which two groups are compared. The observed time rate is taken as well as the expected time rate. These values are put in the formula to calculate the hazard ratio.

Interpreting Hazard Ratios

The hazard ratio is mostly used in medical cases where two groups have to be compared. After there are values for both the groups, there average is calculated. By average, it basically means that the calculation is done over all time scales. The hazard ratio is compared according the numerical value of both of them. If the hazard ratio is 1 then it means there is no difference in survival rates of both the groups. If the hazard ratio is less than one, then it means that there is a reduction in the risk. If it is larger than one, then it means the opposite.