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 that randomly selected person form a population, not having COVID is:

0.999

P(person not having COVID) = 1 - P(person having COVID)

P(F) = 1 - P(E) = 1 - 0.001 = 0.999