document.write( "Question 1127240: Assume that X is normally distributed with a mean ľ = $64. Given that P(X ≥ $75) = 0.2981, we can calculate that the standard deviation of X is? \r
\n" ); document.write( "\n" ); document.write( "I'd like a detailed explanation, please. \r
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Algebra.Com's Answer #743603 by stanbon(75887) $\"\"$ $\"About$

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Assume that X is normally distributed with a mean ľ = $64. Given that P(X ≥ $75) = 0.2981, we can calculate that the standard deviation of X is?
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\n" ); document.write( "If the right tail of X is 0.2981, the left tail is 0.7019
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\n" ); document.write( "Then z = invNorm(0.7019) = 0.5299
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\n" ); document.write( "Using x = z*s + u, solve for \"s\".
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\n" ); document.write( "75 = 0.5299*s + 64
\n" ); document.write( "0.5299s = 11
\n" ); document.write( "s = 20.76
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\n" ); document.write( "To better see what is happening with this problem,
\n" ); document.write( "sketch a normal curve, put 64 as the mean, shade
\n" ); document.write( "the right tail P(x>=75) = 0.2981.
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H. \n" ); document.write( "

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