4. The Graduate Record Exam (GRE) has a combined verbal and quantitative mean of 1000 and a standard deviation of 200. Scores range from 200 to 1600 and are approximately normally distributed. For each of the following problems:

Question

4.	The Graduate Record Exam (GRE) has a combined verbal and quantitative mean of 1000 and a standard deviation of 200. Scores range from 200 to 1600 and are approximately normally distributed. For each of the following problems:

(a)	draw a rough sketch, darkening in the portion of the curve that relates to the answer, and 
(b)	indicate the percentage or score called for by the problem.

a.	What percentage of the persons who take the test score above 1300?
b.	What percentage score above 800?
c.	What percentage score below 1200?
d.	About what score do 20% of the test-takers score?
e.	About what score do 30% of the test-takers score?

PsyDAG · Answer

a, b, c. Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions/probabilities related to the Z scores.

d, e. Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability and its Z score. Insert Z value into above equation and solve for the score. However, you need to designate whether you are talking about higher, lower or ordinate percentage.