Question 628189
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Hi, Re TY, sry on the typo, NORMSDIST(-1.2) = .1151, NORMSDIST is the Excel fucntion used here to detemine the Probability.  
ONe may use a Calculator or z - table to find the Accumulative Probabilities to the left of a particular z-score
the length of pregnancies of humans are normally distributed with a {{{mu}}}= 268 days and {{{sigma}}} = 15 days.
*Note: {{{z = (x - mu)/(sigma)}}}
 P (x < 250) = P ({{{z = (250-268)/15}}} = -1.2)   Excel function: NORMSDIST(-1.2) = .1151