Question

Scores on a common final exam are normally distributed with mean 71 and standard deviation 9. Department policy is that the top 10% of students receive an A. The minimum exam score to be awarded an A is about:

Answer 1

The minimum exam score to be awarded an A is about 8.52.

Explanation:

Let X represent the scores on a common final exam.

It is provided that X follows a normal distribution with mean, μ = 71 and standard deviation, σ = 9.

It is provided that according to the department policy is that the top 10% of students receive an A.

That is, P (X > x) = 0.10.

⇒ P (X < x) = 0.90

⇒ P (Z < z) = 0.90

The corresponding z-score is:

z = 1.28

Compute the value of x as follows:

`z=(x-\mu)/(\sigma)\\\\1.28=(x-71)/(9)\\\\x=71+(1.28* 9)\\\\x=82.52`

Thus, the minimum exam score to be awarded an A is about 8.52.