SOLUTION: IQ scores have a normal distribution with a mean of 100 and a standard deviation of 15. What two IQs separate the middle 95 percent from the remainder of the distribution?

Question 114505: IQ scores have a normal distribution with a mean of 100 and a standard deviation of 15. What two IQs separate the middle 95 percent from the remainder of the distribution?

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
IQ scores have a normal distribution with a mean of 100 and a standard deviation of 15. What two IQs separate the middle 95 percent from the remainder of the distribution?
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The z-scores for a 95% interval centered on the mean is are +/-1.96
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Use the formula z = (x-mu)/sigma to find the appropriate x-scores.
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1.96*sigma = x-mu
1.96*15 = x-100
x = 129.4
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-1.96*sigma = x-mu
-1.96*sigma = x-100
x = 70.6
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Cheers,
Stan H.
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