6. Measures of relative standing (percentiles and quartiles), interquartile range A growth chart is a plot of the percentiles of growth measurements, such as weight and height, for a population of infants or children. It is used by pediatricians to assess a child's growth over time. The Centers for Disease Control and Prevention (CDC) is a U.S. agency devoted to the protection and promotion of public health. Through one of its units, the National Center for Health Statistics (NCHS), the CDC has developed growth charts for clinical use by health professionals. The most recent charts were published in 2000. The 2000 CDC growth charts were developed using a reference population of infants. A pediatrician looks up one of the charts and finds that the 10th percentile for weights of baby girls at 7-1/2 months is 16.5 pounds. This means that of the 7-1/2-month-old baby girls in the reference population weigh 16.5 pounds or less, and of these baby girls weigh 16.5 pounds or more. The 2000 CDC growth charts use a reference population of both breast-fed and formula-fed infants. It has been observed that breast-fed babies tend to gain weight more rapidly than formula-fed babies in the first 2 to 3 months of their lives, but they tend to weigh less than formula-fed babies from 6 to 12 months. Sarah is a healthy baby who was exclusively breast-fed for her first 12 months. Which of the following is most likely a description of her weights (at 3, 6, 9, and 12 months of age) as percentiles of the CDC growth chart reference population? O 10th percentile at 3 months; 40th percentile at 6 months; 75th percentile at 9 months; 95th percentile at 12 months O 75th percentile at 3 months; 85th percentile at 6 months; 95th percentile at 9 months; 95th percentile at 12 months O 65th percentile at 3 months; 35th percentile at 6 months; 30th percentile at 9 months; 20th percentile at 12 months O 30th percentile at 3 months; 30th percentile at 6 months; 30th percentile at 9 months; 30th percentile at 12 months The following are weights (in pounds) for a sample of 11 baby girls at the age of 21 months: 21.9 22.2 23.1 24.4 25.7 26.3 27.5 28.6 29.8 31.5 33.1 The 85th percentile for these sample data is In the sample data, equal to this value. out of 11 observations are less than or equal to the 85th percentile, and out of 11 observations are greater than or For any data set, the first quartile is the third quartile is the percentile. pounds. The third quartile for the prior sample data is percentile, the second quartile is the pounds. ✓ percentile and the ▼, and the