# Normal Distribution

Grades on a midterm exam in a large biochemistry class are normally distributed with a mean of 75 and standard deviation of 9. The instructor wants to assign an A grade to the top 10% of scores, a B grade to the next 10%, and so on, with an F grade to all scores below the 60th percentile. For each letter grade, find the minimum score. What do you think of this grading scheme?

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#### Solution Preview

Grades on a midterm exam in a large biochemistry class are normally distributed with a mean of 75 and standard deviation of 9. The instructor wants to assign an A grade to the top 10% of scores, a B grade to the next 10%, and so on, with an F grade to all scores below the 60th percentile. For each letter grade, find the minimum score. What do you think of this grading scheme?

A grade

Probability= 10% or 0.10

No of tails= 1

Z value corresponding to 0.1 and 1 tail= 1.2816

Mean=M ...

#### Solution Summary

Using Normal distribution, the minimum score for each letter grade is calculated.