Preterm under 37 weeks Low birth weight s under 55 pounds 14

Preterm under 37 weeks Low birth weight s under 5.5 pounds 14 12 Percent of preterm births Percent of low birth weights 1990 1992 1994 1996 1998 2000 2002 Birth Weights in America Mean birth Standard 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 estation period weight deviation 1.88 lb 4.08 b 5.71 lb 644 lb 7.31 lb 7.69 Ib 7.79 lb Under 28 Weeks 1.20 lb rth weight of a baby is related to its gestation period28 to 31 Weeks or a given gestation28 to 31 Weeks 32 to 33 Weeks 37 to 39 Weeks The birth weight of a baby is related to its gestation period 1.85 1b (the time between conception and birth). For a given gestation 132 o 35 weeks I s71bA71b period, the birth weights can be approximated by a normal distribution. The means and standard deviations of the birth 1.47 b 1.19 tb 109 1b 1.04 lb 1.47 1b weeks weights for various gestation periods are shown at the right. One of the many goals of the NCHS is to reduce the percentage 40 Weeks 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 Wecks 42 Weeks and over 41 Weeks 4 i 7.61 lb 1.11 n Exercises 1. The distributions of birth weights for three gestation 2. What percent of the babies born within each periods are shown. Match the curves with the gestation periods. Explain your reasoning period have a low birth weight (under 5.5 pounds)? Explain your reasoning (a) Under 28 weeks(b) 32 to 35 weeks (c) 37 to 39 weeks (d) 42 wecks and over 3. 3, Describe the weights of the top 10% of the babies born with each gestation period. Explain your reasoning (a) 37 to 39 weeks (b) 42 weeks and over Poonds 4. For each gestation period, what is the probability that baby will weigh between 6 and 9 pounds at birth? (a) 32 to 35 weeks (c) 42 weeks and over (b) 37 to 39 weeks 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 (c) 37 to 39 weeks o) Under 28 weeks (b) 32 to 35 wecks 269

Solution

Graph a has mean of 7.69 corresponds to 40 weeks

Graph B has mean 5.71

For 32 weeks mean = 5.71 and spread for 3 sigma =4.41

So graph is for 32 weeks

Graph C:

mean =7.79 std dev = 1.08

Hence 41 weeks