A student takes a true-false test that has 8 questions and guesses randomly at each answer. Let X be the number of questions answered correctly. Find P(6 or more)

Answer 1

Find P(6 or more) implies
P(6) + P(7) + P(8)
= C(8,6)(1/2)^6 (1/2)^2 + C(8,7) (1/2)^8 + C(8,8) (1/2)^8
= (1/2)^8 (28+8+1) = 37/256