10. Guessing Answers Several economics students are unprepared for a multiple-choice quiz with 25 questions, and all of their answers are guesses. Each question has five possible answers, and only one of them is correct.

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m 1 2s m 2 2s m s s

m s continued 228 Chapter 5 Discrete Probability Distributions

a. Find the mean and standard deviation for the number of correct answers for such students.

b. Would it be unusual for a student to pass by guessing and getting at least 15 correct answers? Why or why not?