normal distribution

Question

Assume that adults have IQ scores that are normally distributed with a mean of 105
and a standard deviation equals 20.
Find the probability that a randomly selected adult has an IQ less than 141.

Answer 1

Obtain a z-score chart:

http://www.stat.ufl.edu/~athienit/Tables/Ztable.pdf

 

z = (141 - 105) / 20

z = 36 / 20

z = 1.8

 

Corresponding 96.41%