What is the probability of at least 6 correct answers?

Question

Assume that 8 questions are answered by guessing.
What is the probability of at least 6 correct answers?

Answer 1

₈C₆(0.5)⁶(0.5)² + ₈C₇(0.5)⁷(0.5)¹ + ₈C₈(0.5)⁸(0.5)⁰

 

= 28(0.5)⁸ + 8(0.5)⁸ + 1(0.5)⁸ = 37(0.5)⁸ = 37/256 ≈ 0.1445