Question

Consider a bogus test for a virus that always gives positive results,
regardless of whether the virus is present or not. What is its sensitivity?
What is its specificity? In describing the usefulness of a screening test, why
might it be misleading to say how "accurate" it is by stating its sensitivity
but not its specificity?

Answer 1

Sensitivity is the true positive rate i.e. the rate of correct identification of presence of virus through the test.

Specificity is true negative rate i.e. the rate of correct identification of absence of virus through the test.

Both specificity and sensitivity are very important to conclude a test to be accurate. If we just use sensitivity to regard a test as accurate then many people who do not have the virus might also be tested positive for the presence of virus and can mislead them or threaten them