3. Chris is a very strong student who has an 85% chance of getting an A in any course.

(a) Suppose that Chris takes one course at a time, and decides to keep taking courses until receiving the first non-A, and will quit after the first non-A. [I don't recommend this strategy - it's better to push yourself academically, and take the risk of not being perfect!] In any case, Chris will not take more than 4 courses. What is the expected number of courses Chris will take?

[Hint #1: First write down all the possible values of "the number of courses that Chris will take."

Hint #2: This is not a job for the Np shortcut - think why it isn't.

Hint #3: Draw a tree diagram.]

(b) Write out a specific expected value question related to Chris taking courses, whose answer is

Np = (4 courses)(.85 probability of an A in any given course) = 3.4 As