Enter the sensitivity and specificity into the calculator to determine the likelihood ratio.
Likelihood ratio Formula
The following formula is used to calculate a likelihood ratio.
Positive LR = SE / (100- SP)
Negative LR = (100 - SE) / SP
- Where LR is the likelihood ratio
- SE is the sensitivity
- SP is the specificity
To calculate a positive likelihood ratio, divide the sensitivity by 100 minus the specificity.
In this case, the positive LR tells you how much to increase the probability of having a disease given that someone receives a positive disease test result. Negative LR tells you how much to decrease the probability given a negative test result.
Likelihood Ratio Definition
A likelihood is defined as the probability that a patient has a disease given the result of a test.
Likelihood Ratio Example
How to calculate a likelihood ratio?
- First, determine the sensitivity.
Calculate or measure the sensitivity of the specific test.
- Next, determine the the specificity.
Calculate or measure the specificity of the test.
- Finally, calculate the likelihood ratio.
Calculate the ratio using the equation above.
A likelihood ratio describes the rate or chance that a person has a condition given the result of a specific test.