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A diagnostic test for a particular disease has a sensitivity of 0.90 and a specificity of 0.80. A single test is applied to each subject in the population in which the diseased population is 30%. What is the probability that a person, negative to this test, has no disease?
a) Less than 50%
b) 70%
c) 95%
d) 72%
Correct answer : c) 95%
The probability that a person negative to this test has no disease signifies the Negative predictive value of the test.
A diagnostic test for a particular disease has a sensitivity of 0.90 and a specificity of 0.80. A single test is applied to each subject in the population in which the diseased population is 30%. What is the probability that a person, negative to this test, has no disease?
a) Less than 50%
b) 70%
c) 95%
d) 72%
Correct answer : c) 95%
How to calculate the answer?
Someone kindly post the calculations in a easy to understand method.
assume there are 1000 people .so,there are 300 diseased people among them(as it given prevalence 30%)and who doesn’t have the disease is 700.
so true positve is 270(sensitivity90%)
false negative is 30.
true negative is 560(specificity80%).
false positve is 140.
NEGATIVE PRED; VALUE=(TRUE NEGATIVE/TRUE NEGATIVE+FALSE NEGATIVE)*100
=(560/560+30)*100
=94.9%
assume there are 1000 people .so,there are 300 diseased people among them(as it given prevalence 30%)and who doesn’t have the disease is 700.
so true positve is 270(sensitivity90%)
false negative is 30.
true negative is 560(specificity80%).
false positve is 140.
NEGATIVE PRED; VALUE=(TRUE NEGATIVE/TRUE NEGATIVE+FALSE NEGATIVE)*100
=(560/560+30)*100
=94.9%