COVID-Test
COVID-19 Testing
As pandemic swept across the world, people would often need to get tested for COVID-19 as they travel around. In some parts of the world where covid cases are still rising, a few positive cases a day might have already become the norm. However, in other countries, an entire city might face a lockdown with only a few COVID cases. Either way, getting COVID-19 is a nightmare for most people. While people would get frightened as soon as they receive a positive result, it is worthwhile to take a look at the positivity rate of COVID-19. Just as any other disease, COVID test is not a hundred percent accurate. According to Varsity, most COVID PCR test has a false positive rate of about 5%, similar to the number indicated by Public Health England.
To calculate the possibility of someone having the COVID-19 cases we may deploy the Bayes’ Theorem we learnt in class. Bayes’s Theorem is used to calculate conditional probability — the probability for Event A to take place given a prior event has taken place. The theorem can be defined by the following equation: Given that the probability of a false result is 5%, we may calculate the probability of someone infected by COVID-19 given he/she lives in a city with a COVID-19 positivity rate of 0.1%. : We may observe that in a city with a relatively low rate of COVID infection, even with a positive COVID result, the probability of having the disease is relatively slim.
To combat the risk of false results in COVID-19 testing, many countries conduct multiple PCR tests if a person is tested positive for the first time.
https://www.varsity.co.uk/science/21149