document.write( "Question 851710: the length of all human pregnancies is approximately normal with a mean of 266 days and a standard deviation of 16 days , a) if 20 pregnancies are selected at random, what is the probability that the sample average is less than 260 days? b)if 20 pregnancies are selected at random, what is the probability that the sample mean is within 5 days of the population mean? \n" ); document.write( "

Algebra.Com's Answer #512948 by ewatrrr(24785) $\"\"$ $\"About$

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document.write( "Hi,
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document.write( "mean of 266 days and a standard deviation of 16
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document.write( "Sample of 20,  SD of population = 16/sqrt(20) = 3.5777
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document.write( " = -1.6771 
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document.write( "NORMSDIST(-1.6771)= .0476  0r 4.76%
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document.write( "P(-5/3.5777 ≤ z ≤ 5/3.5777) = P(-1.3975 ≤ z  ≤ 1.3975)
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document.write( "NORMSDIST(-1.3975) = .0811
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document.write( "P(sample mean is within 5 days of the population mean) =  \n" );
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