Question 74645
Lengths  of pregnancies of humans are normally distributed with a mean of 268 days and a standard deviation of 16 days. Use the Emperical Rule to determine the percentage of women whose pregnancies are between 252 and 284 days.
z score =(item-mean)/standard deviation
mean=268, standard deviation=16
For item=252
{{{z=(252-268)/16}}}
{{{z=-16/16}}}
{{{z=-1}}}
For item=284
{{{z=(284-268)/16}}}
{{{z=16/16}}}
{{{z=1}}}
The empirical rule says that
about 68% of all values lie within 1 standard deviation of the mean
about 95% ".......................2................................"
about 99.7% ".......................3.............................."
z=-1 and z=1  they're both 1 standard deviation of the mean, so about 68% of all women have a pregnancy that lasts between 252 and 284 days.
Happy Calculating!!!!