humpf!!
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i don't even know if this is a Beh Sci question...for some reason, i'm not understanding what's being asked...
A 35-year-old woman at 18 weeks' gestation has an increased serum alpha fetoprotein concentration. Which of the following has the greatest influence in
determining the predictive value of this test for neural tube defects?
A) Concentration of alpha fetoprotein in maternal serum
B) Maternal history of monozygotic twin pregnancies
C) Prevalence of neural tube defects in the population in question
D) Sensitivity of the test
E) Specificity of the test
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| mitty
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?C
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| robin082006
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C, prevalence affects PPV
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| star1
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C
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| mjl1717
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Im about 80% sure it has to do with prevalence so I go with answer-c (after the fact)
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| Cedrick
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Sweet
C
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| redj
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I came up with E specificity.
I thought it was asking what increases the + PV of the test. From Goljan, I got increased specificity..so you are confirming disease.
Likewise, increasing sensitivity increases - PV (confirming no disease)
I'm confused about the effect of prevelance on + PV..
Can anyone explain?
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| Diego Casali
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C
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| mjl1717
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PPV and prevalence are directly related
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