Question

Professor Elderman has given the same multiple-choice final exam in his Principles of Microeconomics class for many years. After examining his records from the past 10 years, he finds that the scores have a mean of 76 and a standard deviation of 12.

What is the probability that a class of 15 students will have a class average greater than 70 on Professor Elderman’s final exam?

rev: 11_19_2018_QC_CS-148628, 02_20_2020_QC_CS-201523

Answer 1

This is a normal distribution question with

Sample size (n) = 15

Since we know that

P(x > 70.0)=?

The z-score at x = 70.0 is,

z = -1.9365

This implies that

P(x > 70.0) = P(z > -1.9365) = 1 - 0.02640324627447939

PS: you have to refer z score table to find the final probabilities.

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