document.write( "Question 651322: In a normal distribution 26% of the scores are below 40 and 7% are above 80. Find out the mean and standard deviation of the distribution? \n" ); document.write( "

Algebra.Com's Answer #407705 by stanbon(75887) $\"\"$ $\"About$

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In a normal distribution 26% of the scores are below 40 and 7% are above 80. Find out the mean and standard deviation of the distribution?
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\n" ); document.write( "Find the z-value with a left tail of 0.26
\n" ); document.write( "and the z-value with a left tail of 0.93.
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\n" ); document.write( "invNorm(0.26) = -0.6433
\n" ); document.write( "invNorm(0.93) = 1.4758
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\n" ); document.write( "Create two equations using x = z*s + u
\n" ); document.write( "40 = -0.6433*s + u
\n" ); document.write( "80 = 1.4758*s + u
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\n" ); document.write( "Subtract and solve for \"s\":
\n" ); document.write( "40 = 2.1246s
\n" ); document.write( "s = 40/2.1246 = 18.8272
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\n" ); document.write( "Solve for \"u\":
\n" ); document.write( "u = 40 + 0.6433*18.8272 = 52.11
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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