SOLUTION: If IQ tests have a mean of 100 and standard deviation of 15, what proportion of the population have a) an IQ greater than 120, and b) an IQ less than 70?

Question 505144: If IQ tests have a mean of 100 and standard deviation of 15, what proportion of the population have
a) an IQ greater than 120, and
b) an IQ less than 70?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
If IQ tests have a mean of 100 and standard deviation of 15, what proportion of the population have
a) an IQ greater than 120,
z(120) = (120-100)/15 = 20/15 = 4/3
Prop above 120 = P(z > 4/3) = 0.0912
-------------------
and
b) an IQ less than 70?
z(70) = (70-100)/15 = -2
Prop below 70 = P(z < -2) = 0.0228
=========
Cheers,
Stan H.
=========

RELATED QUESTIONS
IQ scores are normally distributed with a mean of 100 and a standard deviation of 15. If... (answered by stanbon,edjones)

IQ scores are normally distributed with a mean of 100 and a standard deviation of 15. If... (answered by edjones)

if IQ scores are normally distributed with a mean of 100 and a standard deviation of 5,... (answered by robertb)

IQ scores in a general adult population have mean 100 and standard deviation 15. A simple (answered by stanbon)

IQ test scores are randomized to produce a normal distribution with a mean of 100 and a... (answered by stanbon)

Please help! Homework question. A person must score in the upper 2% of the population... (answered by nabla,MathLover1)

B)If IQ scores are normally distributed with a mean of 100 and a standard deviation of... (answered by ewatrrr)

The average IQ is 100. The distribution is normal with a standard deviation of 15. A. (answered by Boreal)

IQ scores are normally distributed with a mean score of 100 and a standard deviation of... (answered by ewatrrr)