document.write( "Question 1155928: Assume newborn baby weights are Normally distributed with a mean of 7.6lbs and a variance of 0.6 lbs. Find the probability a newborn baby weighs over 10lbs or below 8 lbs.\r
\n" ); document.write( "\n" ); document.write( "I know I have to use a z table, but I don't exactly know how \n" ); document.write( "

Algebra.Com's Answer #778634 by Edwin McCravy(20055) $\"\"$ $\"About$

You can put this solution on YOUR website!

\r\n" );
document.write( "We find the z-scores for 10 pounds and for 8 pounds.\r\n" );
document.write( "The standard deviation is the square root of the variance\r\n" );
document.write( " \r\n" );
document.write( "The z-score for 10 pounds:\r\n" );
document.write( "\r\n" );
document.write( "The z-score for 8 pounds:\r\n" );
document.write( "\r\n" );
document.write( "We want to find the fraction, decimal or percent which the shaded area is\r\n" );
document.write( "of the whole area.  Notice that there is very little shading to the right\r\n" );
document.write( "of 3.10 because there are very few babies that weigh more than 10 pounds.\r\n" );
document.write( "In fact you can't even see anything shaded there on the graph below.  But\r\n" );
document.write( "you see 3.10 marked on the z-score axis (the horizontal axis).\r\n" );
document.write( "\r\n" );
document.write( "There are two kinds of tables in use today.  Those with both positive and \r\n" );
document.write( "negative values in the z-column, and those that have only positive values\r\n" );
document.write( "in the z-column.\r\n" );
document.write( "To find the decimal fraction for the shading to the left of z=0.52:\r\n" );
document.write( "If there are negative values in your z-column, then\r\n" );
document.write( "find 0.5 in the z-column and go across to 0.02 and read 0.6985.\r\n" );
document.write( "\r\n" );
document.write( "To find the decimal fraction for the shading to the right of z=3.10:\r\n" );
document.write( "find 3.1 in the z-column and go across to 0.00 (the next column) and read\r\n" );
document.write( "0.9990.  That's the area to the left of 3.10. To find the area to the \r\n" );
document.write( "right of 3.10 subtract from 1.0000, getting 1.0000-0.9990 = 0.0001\r\n" );
document.write( "We add the shading left of 0.52 which is 0.6985 to the tiny shading right of\r\n" );
document.write( "3.10, which is 0.0001 and get 0.6986.\r\n" );
document.write( "-----------------------------\r\n" );
document.write( "If there are only positive values in your z-column, then\r\n" );
document.write( "find 0.5 in the z-column and go across to 0.02 and read 0.1985.\r\n" );
document.write( "That's the shading right of z=0, so add 0.5000 to that and get 0.1985 \r\n" );
document.write( "To find the decimal fraction for the shading to the right of z=3.10:\r\n" );
document.write( "find 3.1 in the z-column and go across to 0.00 (the next column) and read\r\n" );
document.write( "0.4990.  That's the area between z=0 and z=3.10. To find the area to the \r\n" );
document.write( "right of 3.10 subtract from 0.5000, getting 0.5000-0.4990 = 0.0001\r\n" );
document.write( "We add the shading left of 0.52 which is 0.6985 to the tiny shading right of\r\n" );
document.write( "3.10, which is 0.0001 and get 0.6986.\r\n" );
document.write( "Answer: 0.6986\r\n" );
document.write( "But we can only expect the table to be accurate to two decimal places, so we\r\n" );
document.write( "should only claim 0.70 as the answer.\r\n" );
document.write( "The TI-83 or TI-84 gives more accuracy.\r\n" );
document.write( "0.698184662 \r\n" );
document.write( "Edwin

\n" ); document.write( " \n" ); document.write( "

\n" );