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 :
Answer & explanation
Correct answer: option 1
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) = $\frac{1}{100}$