Answer: Find the cumulative probability for 8 in a binomial distribution with n = 20 and p = 0.5.

## Explanation This is a **binomial probability** problem: - **n = 20** (number of trials/questions) - **p = 0.5** (probability of success on each trial, since random guessing) - We want **P(X ≤ 8)** (8 or fewer correct answers) **Why option D is correct:** - The cumulative probability for 8 in a binomial distribution gives P(X ≤ 8), which is exactly what we need - This sums the probabilities of getting 0, 1, 2, ..., 8 correct answers **Why other options are incorrect:** - **Option A**: P(X = 8) only gives the probability of exactly 8 correct answers, not "8 or fewer" - **Option B**: Uniform distribution is inappropriate here; this is a discrete binomial scenario - **Option C**: Normal approximation could be used but is less accurate for small n, and we need cumulative probability, not just P(X = 8)

Author: LeetQuiz Editorial Team