The following would be simpler and more consistent with the beginning of the sentence: “the fraction of sick patients that got a positive result”
Anareth A
Karma: 0
It should be clarified that “the bottom” here refers to the pool.
This sentence should be written above the previous paragraph: 18⁄24 is 3⁄4, not 3⁄7.
“got” would be clearer.