Question 344633
Assume that the duration of a normal human pregnancy can be described by a mean of nine months (270 days) and a standard deviation of one-half month (15 days). Most but not all babies will arrive within two standard deviations of the mean.
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Using x = zs+u, solve for "x".
x = -2*15+270 = 240 days
x = 2*15+270 = 300 days
Therefore, a mother would not expect a baby to arrive sooner 
than 240 days or later than 300 days.
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Cheers,
Stan H.