posted by Susan .
1. A test has a mean of 50, standard deviation of 10.
A. What scores separate the middle 25% from the rest
b. What proportion would be expected to score between 45 and 55
c. What proportion would be expected to score 68 and above
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions and their related Z scores.
A. Find the Z score with .125 between score and mean. Insert ±Z value in the above equation and solve for the scores.
B and C. Solve for Z scores and use the table.