Question

The scores on the Wechsler Adult Intelligence Scale are approximately Normal with μ = 100 and σ = 15.
Reference: Ref 3-4

The proportion of adults with scores between 90 and 110 is closest to
A. 0.250.
B. 0.432.
C. 0.500.
D. 0.667.

Answer 1

I say D.... I'm not 100% how to solve it, I'm bguessing based on what I do know. 1 dev is 68% and 90-100 is a little less than that...

Answer 2

there is also


The proportion of adults with scores above 130 is closest to
A. 0.001.
B. 0.023.
C. 0.050.
D. 0.950.

How high a score is needed to be in the highest 5%?
A. 115.
B. 125.
C. 130.
D. 135.

Which I say B and B

Answer 3

@EulerGroupie

Answer 4

I used a z table.
Starting with \[z=\frac{x-\mu}{\sigma}\]
for the bottom: z=(90-100)/15=-.67
for the top: z=(110-100)/15=.67
look up the values in the z table to get the proportions below the z values
I get 0.2514 and 0.7486 from the z table.