Biostat Q - conquerstep3

[ArchivalUser]

can someone please explain how you got 47%?

[ArchivalUser]

Dis Non Dis total 1000 .10% prevalence 100
+ 80 90 170 PPV=80/170=47%
_ 20 810
100 900 1000

[ArchivalUser]

Are you sure its right? FP=10%

Can someone please explain it?

[ArchivalUser]

Assuming that in a group of 1000 people 10% are (+) for H.Pylori so 100 (are diseased).
From the 100 that are (+) according to the sensitivity of the test 80 are TP and 20 are FN.
From 900 non diseased we have 90% TN = 810 and 10% FP = 90 . Put them in a 2x2 table.

The question is asking PPV so TP/TP + FP , in numbers 80/80+90=0.47 or 47%

Hope this helped

Also my suggestion is to bring up all the situation that we have faced and to resolve them.
Stat looks complicated but boards know that there is not much time for complications in calculation , all we need is practice with them .

[ArchivalUser]

Yes, this is like a question that is in the Kaplan review books, not sure if something exactly like this would be in real exam too much but important to understand it