## Thursday, December 7, 2017

### Likelihood ratio mnemonic

Hello! :)

The likelihood ratio of a positive test result (LR+) is sensitivity divided by 1- specificity.

The likelihood ratio of a negative test result (LR-) is 1- sensitivity divided by specificity.

How I remember the formulae for LR+ and LR-
1) Remembering the numerator and denominator: N / P - You can remember this as N comes before P. I remember this because my name starts with N. So it is seNsitivity / sPecificity.

2) Remembering where the (1 - S) is: The (1-S) is wherever the N or P is. likelihood ratio Negative will have 1 - seNsitivity. likelihood ratio Positive will have 1 - sPecificity.

In summary:
LR+ = Sensitivity / 1 - Specificity
LR - = 1 - Sensitivity / Specificity

That's all!

-IkaN

1. Thanks a lot

2. do we need to know the pretest/posttest probability stuff as well?

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