document.write( "Question 1202109: Scores on the SAT form a normal distribution with a mean score of 500 and a standard deviation of 100. Find the range of scores that defines the middle 80% of the distribution of SAT scores. \n" ); document.write( "
Algebra.Com's Answer #836756 by Theo(13342)\"\" \"About 
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mean is 500
\n" ); document.write( "standard deviation is 100
\n" ); document.write( "z-score with 10% area to the left of it is equal to -1.28
\n" ); document.write( "z-score with 90% area to the left of it is equal to 1.28
\n" ); document.write( "area in between is 80%.
\n" ); document.write( "raw score when z = -1.28 is given by:
\n" ); document.write( "-1.28 = (x - 500) / 100
\n" ); document.write( "solve for x to get x = -1.28 * 100 + 500 = 372
\n" ); document.write( "raw score when z = 1.28 is given by:
\n" ); document.write( "1.28 = (x - 500) / 100
\n" ); document.write( "solve for x to get x = 1.28 * 100 + 500 = 628
\n" ); document.write( "the range of scores that defines the middle 80% os from 372 to 628.
\n" ); document.write( "these are rounded numbers.
\n" ); document.write( "a more exact number would be 371.8448433 to 628.1881867.
\n" ); document.write( "round as required.\r
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