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

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.

## FAQ

**What is a likelihood ratio?**

A likelihood ratio describes the rate or chance that a person has a condition given the result of a specific test.

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