Question

The mean score was 72%. The standard deviation was 7%. Based on this information, what is the best approximation for the number of students who scored 80% or better?

Answer 1

Assuming scores (denoted by the random variable
`X`) are normally distributed, we can say


`\mathbb P(X\ge80)=\mathbb P\left(\frac{X-72}7\ge\frac{80-72}7\right)\approx\mathbb P(Z\ge1.143)\approx0.1265`

where
`Z` has the standard normal distribution. So if there are
`n` students, we can expect approximately 12.65% of them to have a score of at least 80%.

Answer 2

Option B. 159, is the correct answer

Explanation: