A coin is tossed 4 times and the sequence of heads and tails is observed.
a. What is the probability that heads and tails occur equally often if the coin is fair and the tosses are independent?
b. Now suppose the coin is loaded so the P(H) =1/3 and P(T) = 2/3 and that the tosses are independent. What is the probability that heads and tails occur equally often, given that the first toss is a head?