Question 581441
Dorians score of 572 on the normally distributed verbal portion of the 1996 SAT exam placed him at the seventy third percentile. If the mean on this exam was 505, what was the standard deviation? 
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The 73rd%ile score has a left tail of 73%
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Find the corresponding z-value:
invNorm(0.73) = 0.6128
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Then use x = z*s + u to solve for "s":
572 = 0.6128*s + 505
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67 = 0.7128s
s = 109.33
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Cheers,
Stan H.