new_n_lost
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Researchers are assessing the specificity of a screening procedure for breast cancer in a population of 3000 women whose mothers had the disease. The presence or absence of a malignant condition is established by conventional mammography, which is assumed to be definitive for the purposes of comparison.
The following data are collected:
Positive Negative Total
Cancer 90 10 100
No cancer 360 2540 2900
Total 450 2550 3000
What is the specificity of the test?
A. 90/100
B. 90/450
C. 2540/2550
D. 2540/2900
E. (90+2540)/3000
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"never argue with a fool, they'll bring you down to their level and beat you with experience" FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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| sprint123
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d..
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| robin082006
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D, so easy
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| new_n_lost
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 .
Yes i wish they ask like this in the Exm.
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"never argue with a fool, they'll bring you down to their level and beat you with experience" FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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| new_n_lost
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The correct answer is D.
Specificity refers to how well a test identifies persons who do not have the disease in question. In the example, 2900 women do not have breast cancer, and 2540 of these women have a negative test. Specificity is given by (true negatives)/ (true negatives + false positives) = 2540/(2540+360) = 2540/2900.
Choice A, 90/100, represents the sensitivity of the test; that is, the proportion of women with the condition who test positive.
Choice B, 90/450, gives the predictive value of a positive test. Of the 450 women who tested positive, 90 actually had the condition.
Choice C, 2540/2550, gives the predictive value of a negative test. Of the 2550 who tested negative, 2540 did not have cancer.
Choice E, (90+2540)/3000, refers to the efficiency of a test; that is, the proportion of all subjects who were correctly classified by the test.
___________________
"never argue with a fool, they'll bring you down to their level and beat you with experience" FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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| dowitesrgreat
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ans is D, but it took more than one minute to solve ,!
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