At a certain college, 15% of the students receieved an A in their required math cousre, 10% receieved an A in their required chemistry course, and 5% receieved an A in both. A student is selected at random.

Question

a.) What is the probability that he received an A in either chemistry or math?

b.) What is the probabilty that he receieved an A in chemistry, if he ahd an A in math?

c.) what is the probaility that he receieved an A in math, if he had an A in chemistry?

d.) Are th events " A in math" and "A in chemistry" independent?

Answer 1

Draw a venn diagram.

a) P(C or M) = P(C)+P(M)-P(C and M) = .10 + .15 - .05 = 20%

b) 15% got an A in Math, 5% both, or 33.33% of those that got an A in Chem.

c) repeat logic in b)

d) if they were independent, the prob of getting A's in both would be P(C)*P(M)

Answer 2

In a bank call center, it is determined over a one year period that 30% of the outgoing calls are answered by a live person as opposed to being unanswered or picked up on voice mail. The center makes over 200,000 outgoing calls per year. there is an operator at the center who places 25 outgoing calls in a one hour period. What is the probability that this operator will get live answers on 7 or more calls

Answer 3

A blood donor center conducted a study over a one year period and found that an average of 55 donors per day checked in to the center. What is the probability that on any given day more than 75v donors will check in?