Estimate the indicated probability by using the normal distribution as an approximation to the binomial distribution.
-A multiple choice test consists of 60 questions. Each question has 4 possible answers of which one is correct. If all answers are random guesses, estimate the probability of getting at least 20% correct.
A) 0.8508
B) 0.0901
C) 0.1492
D) 0.3508

Question

Quizplus · Accepted Answer

The probability of guessing a question correctly is 0.25. For 60 questions, the mean is 15 and the standard deviation is 3.35. Using the normal approximation, we find the probability of getting at least 12 correct (20% of 60) is approximately 0.8508.

Estimate the Indicated Probability by Using the Normal Distribution as an Approximation