11-06-2010, 11:02 AM
tc10,
You are very welcome .
It is good to "see" you again
You are very welcome .
It is good to "see" you again
Biostatistics Q.......2 - psychmledr
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11-06-2010, 11:02 AM
tc10,
You are very welcome . It is good to "see" you again
12-24-2013, 05:46 PM
Bump
12-25-2013, 11:59 AM
thanks mledr. brilliant question.
is there a shorter way of arriving at answer? creating table looks like it can take me over a minute if this were to appear in an exam
12-25-2013, 12:24 PM
here is the formula PPV=sensitivity*prev/sensitivity*prev + (100-specificity)*(100-prevalence) NPV=specificity*(100-prevalence)/specificity*(100-prevalence) +(100-sensitivity)*prevalence http://www.usmleforum.com/showthread.php?tid=753272-1
12-25-2013, 12:32 PM
Try this Qs
Q1) In a poor, small village you use a new, cheap lab test X to rule out the possibility of TB. A pt from this village has persistent cough and comes to your temporary clinic to check for TB. His result is negative. Test X has a specificity of 80% and a sensitivity of 90% when tested in 100 subjects with TB and 100 subjects without TB in this village. What is the probability that this patient truly does not have TB? A. 18% B. 53% C. 66% D. 82% E. 89% Q2) In a poor, small village a cross-sectional study with a viral RNA shows that 20% of the people are HIV positive. You discover a new cheap diagnostic kit to test for HIV in this village. this test has a specificity of 80% and a sensitivity of 90%. This test was positive in one of the patients from the village. What is the best estimate of the likelihood that this patient has actually HIV?
12-25-2013, 04:02 PM
Q1) E
Q2) 53% |
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