Question

Select the correct answer.
The probabilities of a test are represented by I for infected; U, uninfected; D, infection detected; and N, no infection detected. What is the symbolic way to represent the probability of a true positive?

A.

B.

C.

D.

Answer 1

The event "true positive" is that the person is infected and the test detects it, so symbolically:
P(I ∩ D) (equivalently P(D ∩ I)).

(If you meant the true positive rate / sensitivity, that's P(D | I) = P(I ∩ D)/P(I).)