Probabilty question nunber 4

Question

A psychology class has 28 males and 52 females. If the professor selects names from the class list using random sampling.

a. What is the probability that the first student selected will be a female?

b. If a random sample of n=3 students is selected and the first two are both females, what is the probability that the third student selected will be a male?

Answer 1

There are 28 + 52 or 80 total members in the class so the probability that a randomly selected person will be a female is 52/80 or (reduced) 13/20.

If the first selection was a female, then there are now 28 males and 51 females (a total of 79) to select from. If the second selection was a female, then there are now 28 males and 50 females (a total of 78) to select from. So for the third selection, the probability of randomly selecting a male is 28/78 or (reduced) 14/39.