There are five multiple-choice questions on an exam, each having responses a, b, c, or d. Each question is worth 5 points and only one option per question is correct. Suppose a student guesses the answer to each question, and his or her guesses from question to question are independent. The student's mean number of questions correct on the exam should be ______.

A. 1.25
B. 2.5
C. 6.25

Correct Answer: A

X, the number correct if you were guessing, has the binomial distribution with parameters n = 5 and p = 0.25. The mean of X is u = np = 1.25.