Question

In 2009, the national average for the math portion of the College Board's SAT is 515. The College Board periodically rescales the test scores such that the standard deviation is approximately 100. Given that the distribution is bell-shaped, what percentage of students have an SAT math score greater than 715? a. approx 2.5% b. approx 68% c. approx 95% d. none of the above

Answer 1

D; none of the above

Explanation:

We start by calculating the z-score of the 715 score

Mathematically;

z-score = (x - mean)/SD

from the question, x = 715, mean = 515 , SD = 100

Substituting these;

(715-515)/100 = 200/100 = 2

So the probability we want to calculate is;

P(Z > 2)

We are going to use normal distribution table for this;

P(z > 2) = 0.02275

0.02275 in percentage is 2.275%

Correct t answer is none of the above