2. Sample Papers
  3. JEE Main & Advanced

JEE Main & Advanced Sample Paper JEE Main Sample Paper-12

  • question_answer
    One percent of the population suffers from a certain disease. There is blood test for this disease, and it is 99% accurate, in other words, the probability that it gives the correct answer is 0.99, regardless of whether the person is sick or healthy. A person takes the blood test, and the result says that he has the disease. The probability that he actually has the disease, is

    A)  0.99%                  

    B)  25%

    C)  50%                                      

    D)  75%

    Correct Answer: C

    Solution :

     A: blood result says positive about the disease \[{{\text{B}}_{\text{1}}}\]: Person suffers from the disease\[\therefore \]\[P({{B}_{1}})=\frac{1}{100}\] \[{{\text{B}}_{\text{2}}}\]: person does not suffer\[\therefore \]\[P({{B}_{2}})=\frac{99}{100}\] \[P(A/{{B}_{1}})=\frac{99}{100},P(A/{{B}_{2}})=\frac{1}{100}\] \[P({{B}_{1}}/A)=\frac{P({{B}_{1}}).P(A/{{B}_{1}})}{P({{B}_{1}}).P(A/{{B}_{1}})+P({{B}_{2}}).P(A/{{B}_{2}})}\] \[=\frac{\frac{1}{100}.\frac{99}{100}}{\frac{1}{100}.\frac{99}{100}+\frac{99}{100}.\frac{1}{100}}=\frac{99}{2.99}=\frac{1}{2}=50%\]


You need to login to perform this action.
You will be redirected in 3 sec spinner