Question

1) There are two more assignments in your course before the semester ends, and if you get an A on at least

one of them, you will get an A for the semester. Your "what-if" scenario looks like this:

Event Probability

A on paper and A on presentation .25

A on paper only .10

A on presentation only .20

Do not get an A on either .35

Answer the following questions: (1 point each, except the last item, 2 points)

1a) What is the probability of getting an A on the paper?

1b) What is the probability of getting an A on the presentation?

1c) What is the probability of getting an A in the course?

1d) Are the grades on the assignments independent? Explain your answer

Answer 1

In this, the sum of the probabilities of all the possible events is equal to

0.25 + 0.10 + 0.20 + 0.35 = 0.90 (i.e not equal to 1)

Thus the probability distribution is incorrect

If we assume it to be correct, the required probabilities are

(a) Probability of getting an A on the paper = Probability of getting an A on paper only + Probability of getting an A on paper and A on presentation = 0.10 + 0.25 = 0.35

(b) Probability of getting an A on the presentation = 0.20 + 0.25 = 0.45

(c) Probability of getting an A in the course = 0.25 + 0.10 + 0.20 = 0.55

(d) No, the grades on the assignment are not independent

Since P(getting A on paper and A on presentation) ≠ P(getting A on paper) * P(getting A on presentation)

(0.45*0.55 = 0.2475 ≠ 0.25)