SOLUTION: Assume that adults have IQ scores that are normally distributed with a mean of 100.1 and a standard deviation 20.5. Find the first quartile Upper Q 1​, which is the IQ score sepa

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Question 1135421: Assume that adults have IQ scores that are normally distributed with a mean of 100.1 and a standard deviation 20.5. Find the first quartile Upper Q 1​, which is the IQ score separating the bottom​ 25% from the top​ 75%. (Hint: Draw a​ graph.)
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
z=(x-mean)/sd
z for 0.2500 probability is -0.675
-0.675=(x-100.1)/20.5
x=86.26 Q1
Q3 is the same distance on the other side
x=113.94 Q3. That is the upper quartile. The phrasing of the question is a little ambiguous here.