<PRE><B>Question 916901</B>
Suppose there is an IQ test with a mean score of 95 and a standard deviation of 4.3. If we would like to target some advertising to the middle 60% of the population, what are the cutoff IQ scores on this test?
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Draw a picture of a normal curve with 60% centered on the mean.
The left tail is 0.20
Find the z-score with a left-tail of 20%::
invNorm(0.20 ) = -0.8416
Find the z-score with a right-tail of 20%::
z = +0.8416
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Find the corresponding scores::
x = -0.8416*4.3 + 95 = 91.38
x = +0.8416*4.3 + 95 = 98.62
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Cheers,
Stan H.
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