Several psychology students are unprepared for a surprise true/false test with 1
ID: 3176248 • Letter: S
Question
Several psychology students are unprepared for a surprise true/false test with 15 questions, and all of their answers are guesses. Find the mean and standard deviation for the number of correct answers for such students. Would it be unusual for a student to pass by guessing (which requires getting at least 12 correct answers)? Why or why not? mu = sigma (Round to one decimal place as needed.) Choose the correct answer below. No, because 12 is within the range of usual values. Yes, because 12 is greater than the maximum usual value. Yes, because 12 is below the minimum usual value. Yes, because 12 is within the range of usual values.Explanation / Answer
p = 0.5
n = 15
A) mean = n * p = 15*0.5 = 7.5 or 8
Standard deviation = sqrt (n*p*(1-p)) = sqrt(15*0.5*0.5) = 1.9
B) P(X = 12) = 15C12 * 0.512 * 0.515-12
= 0.0139
Option-c) yes because 12 is below the minimum usual value