IQ scores based on the Wechsler Adult Intelligence Scale are assumed to be normally distributed with a mean of 100 and a standard deviation of 15. What is the z-score for an IQ of 90?
A) z = -.67
B) z = .67
C) z = -10
D) z = 12.67

Question

Quizplus · Accepted Answer

To find the z-score, we use the formula:

z = (x - μ) / σ

Where x is the raw score (in this case, 90), μ is the mean (100), and σ is the standard deviation (15).

Plugging in the values, we get:

z = (90 - 100) / 15
z = -0.67

Therefore, the z-score for an IQ of 90 is -0.67, which corresponds to choice A.

IQ Scores Based on the Wechsler Adult Intelligence Scale Are