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, 
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.
=========