Birth Weights in America

The National Center for Health Statistics (NCHS) keeps records of many health-related aspects of people, including the birth weights of all babies born in the United States.

The birth weight of a baby is related to its gestation period (the time between conception and birth). For a given gestation period, the birth weights can be approximated by a normal distribution. The means and standard deviations of the birth weights for various gestation periods are shown at the right.

One of the many goals of the NCHS is to reduce the percentage of babies born with low birth weights. As you can see from the graph at the upper right, the problem of low birth weights increased from 1990 to 2004.

1. The distributions of birth weights for three gestation periods are shown. Match the curves with the gestation periods. Explain your reasoning.

2. What percent of the babies born within each gestation period have a low birth weight (under 5.5 pounds)? Explain your reasoning.

1. Under 28 weeks (b) 32 to 35 weeks
   (c) 37 to 39 weeks (d) 42 weeks and over
   3. Describe the weights of the top 10% of the babies born
   with each gestation period. Explain your reasoning.
   1. 37 to 39 weeks (b) 42 weeks and over

4. For each gestation period, what is the probability that

a baby will weigh between 6 and 9 pounds at birth?

1. 32 to 35 weeks (b) 37 to 39 weeks

(c) 42 weeks and over

5. A birth weight of less than 3.3 pounds is classified by

the NCHS as a "very low birth weight." What is the

probability that a baby has a very low birth weight

for each gestation period?

(a) Under 28 weeks (b) 32 to 35 weeks (c) 37 to 39 weeks

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Solution: The downloadable solution consists of 7 pages, 512 words and 3 charts.
Deliverable: Word Document