document.write( "Question 1074409: I hope this is in the right category. \r
\n" ); document.write( "\n" ); document.write( "The monthly salaries in a company with 5000 employees are normally distributed. The mean salary is $3100 with a standard deviation of $700. What percentage of employees earn more than $2400 per month? How many employees earn more than $2400 per month?
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Algebra.Com's Answer #689107 by Theo(13342)\"\" \"About 
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mean is 3100
\n" ); document.write( "standard deviation is 700.\r
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\n" ); document.write( "\n" ); document.write( "2400 is (3100 - 2400) / 700 = 1 standard deviation from the mean in a negative direction.\r
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\n" ); document.write( "\n" ); document.write( "that makes the z-score equal to -1.\r
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\n" ); document.write( "\n" ); document.write( "with z-scores, the mean is 0 and the z-score is the number of standard deviations away from the mean.\r
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\n" ); document.write( "\n" ); document.write( "the formula is z = (x-m) / s\r
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\n" ); document.write( "\n" ); document.write( "z is the z-score
\n" ); document.write( "x is the raw score
\n" ); document.write( "m is the mean
\n" ); document.write( "s is the standard deviation.\r
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\n" ); document.write( "\n" ); document.write( "the formula becomes z = (2400 - 3100)/700 = -700/700 = -1\r
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\n" ); document.write( "\n" ); document.write( "to find the percentage of employees that earn more than a z-score of -1, look up in the z-score table for a rate (rate = % / 100) to the left of a z-score of -1.\r
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\n" ); document.write( "\n" ); document.write( "then take 1 minus that rate for a rate to the right of a z-score of -1.\r
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\n" ); document.write( "\n" ); document.write( "if you used the table linked to below, you would have found the rate to the left of the z-score of -1 equal to .1587 and then gotten the rate to the right of the z-score of -1 equal to 1 - .1587 = .8413.\r
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\n" ); document.write( "\n" ); document.write( "http://www.stat.ufl.edu/~athienit/Tables/Ztable.pdf\r
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\n" ); document.write( "\n" ); document.write( "alternatively use a calculator that goes normal distribution type problems.\r
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\n" ); document.write( "\n" ); document.write( "i used the following calculator.\r
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\n" ); document.write( "\n" ); document.write( "http://davidmlane.com/hyperstat/z_table.html\r
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\n" ); document.write( "\n" ); document.write( "if allows me to find the rate to the left of or to the right of a particular z-score or in between 2 z-scores or outsides of 2 z-scores.\r
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\n" ); document.write( "\n" ); document.write( "very nice calculator.\r
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\n" ); document.write( "\n" ); document.write( "i got a rate of .8413\r
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\n" ); document.write( "\n" ); document.write( "that means that 84.13% of the employees earn more than 2400 per month.\r
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\n" ); document.write( "\n" ); document.write( "the number of employees that earn more than 2400 per month would be equal to 5000 * .8413 = 4206.5 which would be rounded to 4206 or 4207.\r
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\n" ); document.write( "\n" ); document.write( "by convention of mathematical rounding rules, you would round to 4207.\r
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\n" ); document.write( "\n" ); document.write( "the same calculator can be used with raw scores or z-scores.\r
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\n" ); document.write( "\n" ); document.write( "with z-scores, mean is 0 and standard deviation is 1.\r
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\n" ); document.write( "\n" ); document.write( "with raw scores, mean is 3100 and standard deviation is 700.\r
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\n" ); document.write( "\n" ); document.write( "results are shown below:\r
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\n" ); document.write( "\n" ); document.write( "the same calculator can be used to find the area from the z-score or the z-score from the area.\r
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\n" ); document.write( "\n" ); document.write( "it can do the same using the raw mean score and standard deviation as well.\r
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\n" ); document.write( "\n" ); document.write( "nice calculator.\r
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\n" ); document.write( "\n" ); document.write( "even gives you a picture of the area under the distribution curve that it calculated for you.\r
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\n" ); document.write( "\n" ); document.write( "use of the table rather than the calculator would have given you a result as shown below.\r
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\n" ); document.write( "\n" ); document.write( "it's more work, but you get the same answer if you do it right.\r
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\n" ); document.write( "\n" ); document.write( "the row heading would -1.0 and the column heading would be .00\r
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\n" ); document.write( "\n" ); document.write( "add them together and you get a z-score of -1.00.
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