Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Probability

Question:

It is given that only 0.1 % of a large population have COVID infection. In this population, the reliability of COVID RTPCR-test is specified as follows :

For persons having COVID, 90% of the test detects the disease but 10% goes undetected. For persons not having COVID, 99% of the test is judged COVID negative but 1% are diagnosed as COVID positive.

Based on the above informations, answer the question :

The probability of the person to be tested as COVID positive, given that he is actually not having COVID is :

Options:

$\frac{1}{100}$

$\frac{9}{10}$

$\frac{1}{10}$

$\frac{99}{100}$

Correct Answer:

$\frac{1}{100}$

Explanation:

Let A = Person selected has covid.

B = Person don't have covid.

C = Person have judge report positive.

P(Tested COVID positive / does not has COVID) = 1% i.e. $\frac{1}{100}$

P(C/A) = $\frac{1}{100}$