# Question: Birth weights in the United States have a distribution that

Birth weights in the United States have a distribution that is approximately normal with a mean of 3369 g and a standard deviation of 567 g (based on data from “Comparison of Birth Weight Distributions between Chinese and Caucasian Infants,” by Wen, Kramer, Usher, American Journal of Epidemiology, Vol. 172, No. 10).
a. One definition of a premature baby is that the birth weight is below 2500
g. If a baby is randomly selected, find the probability of a birth weight below 2500 g.
b. Another definition of a premature baby is that the birth weight is in the bottom 10%. Find the birth weight that is the cutoff between the bottom 10% and the top 90%.
c. A definition of a “very low birth weight” is one that is less than 1500
g. If a baby is randomly selected, find the probability of a “very low birth weight.”
d. If 25 babies are randomly selected, find the probability that their mean birth weight is greater than 3400 g.

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