Standardized tests: In a particular year, the mean score on the ACT test was 21.
ID: 3297643 • Letter: S
Question
Explanation / Answer
Part 1:
mu = 21.8 and sigma = 5.7
z-score for x=16 can be calculated using central limit theorem
z = (x - mu)/sigma = (16 - 21.8)/5.7 = -1.0175
Part 2:
mu = 533 and sigma = 121
z-score for x=524 can be calculated using central limit theorem
z=(x-mu)/sigma = (524 - 533)/121 = -0.0744
Part 3:
mu = 21.8 and sigma = 5.7
for z=2.02, find x using central limit theorem
z = (x - mu)/sigma
x = z*sigma + mu = 2.02*5.7 + 21.8 = 33.314
Part 4:
mu = 533 and sigma = 121
for z=-0.9, find x using central limit theorem
z = (x - mu)/sigma
x = z*sigma + mu = -0.9*121 + 533 = 424.1