assume adults have an IQ score that are normally distrubted with a mean of 105 and standard deviation of 20

Question

A) find the percentage of adults that have an IQ between 94 and 116
B) find the percentage of adults IQ exceeding 120
C)Determine the 1st, 2nd, and 3rd quartiles for adults IQ
D) obtain the 95th percentile

Answer 1

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions related to the Z scores.

Reverse the process for the last two problems.

first Quartile = 25 percentile or lowest 25%

Second quartile = mean in normal distribution.

3rd quartile = lowest 75% percentile

Answer 2

0.3025