| Author | 6 Posts |
nadiabarati
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The probability of Hepatitis B P(D+) in a certain pt population is known to be 0.20 ,conversely P(D-)=0.80 .In a study of new diagnositc test for Hepatitis B, the probability of positive test result among pt's known to have hepatitis B ,P(T+(D+), is shown to be 0.90.,where as probability that healthy pt will have negative result ,P(T-(D-), is shown to be 0.95 .What is the probability that a new pt with a negative test is truly healthy ? A. 0.95 B. 0.95 X 0.80
( 0.95 X 0.80) +(0.5 X0.80) C. .95 X.20
( .95 X.80 )+(.90 X 0.20) D. .95 X.80
( .95 X .80)+(.90 X.20)
E.none
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| nadiabarati
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I think the answer is 76/78
it means E.none
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| robin082006
Forum Hero
Topics: 471
Posts: 5,125
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This q asls about Negative Predictive Value
I have posted the way to calculate it twice in this forum.
ANswer is 76/78, so E.
......................Disease .....................Non-Disease..................... Total
Positive...........18.............................4...................... ..............22
Negative...........2.............................76 ....................................78
Total...............20.............................80.................... ..............100
NPV=76/68
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The Key to Succeed is Patience.
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| malignant
Topics: 2
Posts: 24
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Hi Robin,
This makes me feel stupid,
but still i couldn't figure out how you calculated TP,FP,TN,FN
I will really really appreciate if You can explain again please.
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| smal
Forum Guru
Topics: 140
Posts: 727
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i calculated it as 95/98.....
see TN is .95
TP is .9.....so FP will be .2-(.2x.9)
TN predictive value is TN/TN+FN
hence 95/97.
comments most welcomed
___________________
remedy for weakness is not brooding over it ,but thinking of strength.
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| smal
Forum Guru
Topics: 140
Posts: 727
|
i calculated it as 95/98.....
see TN is .95
TP is .9.....so FP will be .2-(.2x.9)
TN predictive value is TN/TN+FN
hence 95/97.
comments most welcomed
___________________
remedy for weakness is not brooding over it ,but thinking of strength.
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