In: Statistics and Probability
67. Suppose that P(B) = 0.4, P(A|B) = 0.1 and P(A|B^c) = 0.9
(a) Calculate P(A)
(b) Calculate P(A|B)
71. Suppose a couple decides to have three children. Assume that the sex of each child is independent, and the probability of a girl is 0.48, the approximate figure in the US.
(a) How many basic outcomes are there for this experiment? Are they equally likely?
(b) What is the probability that the couple has at least one girl?
104. A multiple-choice quiz has 12 questions, each of which has 5 choices. To pass you need to get at least 8 of them correct. Nina forgot to study, so she simply guesses at random.
Let the random variable X denote the number of questions that Nina gets correct on the quiz. What kind of random variable is X? Specify all parameter values.
Calculate the probability that Nina passes the quiz.