Enter the incidence rate in the exposed and unexposed groups into the calculator to determine the incidence density ratio.



  • Incidence Density Calculator


Incidence Density Ratio Formula


The following formula is used to calculate the incidence density ratio for a given set of incidence rates. 


IDR = IR<sub>e</sub> / IR<sub>u</sub>


Variables:




  • IDR is the incidence density ratio

  • IRe is the incidence rate in the exposed group

  • IRu is the incidence rate in the unexposed group


To calculate the incidence density ratio, divide the incidence rate in the exposed group by the incidence rate in the unexposed group.


What is an Incidence Density Ratio?


The incidence density ratio (IDR) is a measure used in epidemiology to compare the incidence rates of a particular event or disease between two groups. One group is typically exposed to a certain factor, while the other group is not. The IDR helps in understanding the relative risk of the event or disease occurring in the exposed group compared to the unexposed group. A higher IDR indicates a greater risk in the exposed group, while an IDR of 1 suggests no difference in risk between the two groups.


How to Calculate Incidence Density Ratio?


The following steps outline how to calculate the Incidence Density Ratio.




  1. First, determine the incidence rate in the exposed group (IRe).

  2. Next, determine the incidence rate in the unexposed group (IRu).

  3. Finally, calculate the Incidence Density Ratio using the formula IDR = IRe / IRu.

  4. After inserting the values and calculating the result, check your answer with the calculator above.



Example Problem : 


Use the following variables as an example problem to test your knowledge.


Incidence rate in the exposed group (IRe) = 0.05


Incidence rate in the unexposed group (IRu) = 0.02