Question

The grades on the last science exam had a mean of 89%. Assume the population of grades on science exams is known to be distributed normally, with a standard deviation of 14%. Approximately what percent of students earn a score between 75% and 89%?

Answer 1

Are you sure the standard deviation is 14% = 0.14? I'll assume it is.

$\mathbb P(75<X<89)=\mathbb P\left(\dfrac{75-89}{0.14}<\dfrac{X-89}{0.14}<\dfrac{89-89}{0.14}\right)=\mathbb P(-100<Z<0)\approx0.5$

I suspect the given standard deviation is wrong, and that you instead meant 14 (no percent). This would make the probability

$\mathbb P(75<X<89)=\mathbb P\left(\dfrac{75-89}{14}<\dfrac{X-89}{14}<\dfrac{89-89}{14}\right)=\mathbb P(-1<Z<0)\approx0.3413$

which seems a more likely answer.

Answer 2

Answer:

B. 34%

Step-by-step explanation:

took the test got it right