SOLUTION: IQ test scores are randomized to produce a normal distribution with a mean of 100 and a standard deviation of 15. Find the proportion of the population in each of the following: a

Question 457458: IQ test scores are randomized to produce a normal distribution with a mean of 100 and a standard deviation of 15. Find the proportion of the population in each of the following:
a. IQ greater than 140
b. IQ from 120-140
c. IQ 90-109
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
IQ test scores are randomized to produce a normal distribution with a mean of 100 and a standard deviation of 15. Find the proportion of the population in each of the following:
a. IQ greater than 140
z(140) = (140-100)/15 = 40/15 = 8/3
P(x > 140) = P(z > 8/3) = 0.00383
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b. IQ from 120-140
z(120) = (120-100)/15 = 20/15 = 4/3
P(120< x <140) = P(4/3< z <8/3) = 0.08738
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c. IQ 90-109
z(90) = -10/15 = -2/3
z(109) = 9/15 = 3/5
P(90 < x < 109) = P(-2/3 < z < 3/5) = 0.4733
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Cheers,
Stan H.
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