That is: the prior odds are $~$1 : 100,000$~$ against HIV, and a positive result in an initial screening favors HIV with a likelihood ratio of $~$500 : 1.$~$

It would be nice to show how to go from 99.8% to the 500:1 ratio.

by yassine chaouche Jun 11 2017

That is: the prior odds are $~$1 : 100,000$~$ against HIV, and a positive result in an initial screening favors HIV with a likelihood ratio of $~$500 : 1.$~$

It would be nice to show how to go from 99.8% to the 500:1 ratio.