Question

you are taking a quiz with 10 true-false questions. What is the probability that you will be able to choose a random answer on every question and get 9 or 10 correct answers?

Answer 1

n=10

p=1/2 =0.5

q=1-0.5 =0.5

P=nCr p^r q^(n-r)

P(x=9 or 10) = P(x=9) + P(x=10)

                    =10C9 (0.5)^9 (0.5)^(10-9) + 10C10 (0.5)^10 (0.5)^(10-10)

                    =(5/512) + (1/1024)

                    =0.0107