Describe what the notation upper p left parenthesis upper b vertical line upper a right parenthesis represents. choose the correct answer below. a. the probability of event a occurring, given that event b has already occurred. b. the probability of event b occurring, given that event a has already occurred. c. the probability of event b or event a occurring. d. the probability of event b and event a occurring

The correct answer is b), the probability of B occurring given A has occurred.

The correct choice is B.

When you have a vertical line in a probability statement, it is referring to the fact that the second event has already happened.

Imagine, drawing marbles from a bag of blue and red marbles. You could write a probability statement in which you asked, "What is the probability of drawing a red marble given that you just drew a blue marble?" 

In this case, you would use a vertical line separating the two events.