3. Measures of location Percentiles and quartiles Aa Aa A growth chart is a plot

Question

3. Measures of location Percentiles and quartiles Aa Aa 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 97th percentile for weights of baby girls at 8-1/2 months is 24.8 pounds. This means that of the 8-1/2-month-old baby girls in the reference population weigh 24.8 pounds or less, and of these baby girls weigh 24.8 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 25th percentile at 3 months; 25th percentile at 6 months; 25th percentile at 9 months; 25th percentile at 12 months O 85th percentile at 3 months; 85th percentile at 6 months; 90th percentile at 9 months; 95th percentile at 12 months O 30th percentile at 3 months; 50th percentile at 6 months; 70th percentile at 9 months; 80th percentile at 12 months O 75th percentile at 3 months; 40th percentile at 6 months; 25th percentile at 9 months; 25th percentile at 12 months The following are weights (in pounds) for a sample of 11 baby boys at the age of 25 months: 22 23.4 24.8 25.4 26.5 27.9 28.7 29.6 30.1 31.2 33.3 The 70th percentile for these sample data is pounds In the sample data observations are greater than or equal to this value out of 11 observations are less than or equal to the 70th percentile, and out of 11 For any data set, the first quartile is the percentile, the second quartile is the percentile and the , and the third quartile is the percentile In the prior sample data, the first quartile is interquartile range is pounds, and the third quartile is Therefore, the

Explanation / Answer

A pediatrician looks up one of the charts and finds that the 97 percentile for wights of baby girls at 8-1/2 months is 24.8 pounds.

This means that 97% of the 8-1/2 months old baby girls in the reference population weigh 24.8 pounds or less, and 3% of these baby girls weigh 24.8 pounds or more.

Since the percentile indicates the value below which the given percentage of observations falls.

For Second Case:

The most likely description of sarah's weight (at 3,6,9 and 12months of age) as percentile of CDC growth chart.

A) 25th percentile at 3 months, 25th percentile at 6 months,25th percentile at 9 months,25th percentile at 12 months.

Since at the 12th month the percentage of weight will be 100%. Therefore the data should include all the percentile.

The weight for a sample of 11 baby boys at the age of 25 months:

22,23.4,24.8,25.4,26.5,27.9,28.7,29.6,30.1,33.3

We need to find 70th percentile.

heren=11

therefore the 70th percentile is =0.70*11=7.7 =8 th observation.

70th percentile is =29.6 pounds.

n a sample data 8 out of 11 observations are less than 70th percentile, and 3 out of 11 observation are greater than 70th percentile.

For any data, the first quartile is 25th percentile, the second quartile is 50th percentile, and the median, the third quartile is 75th perentile.

In the prior sample data, the first quartile is=24.8 pounds, second quartile=27.9 pounds, third quartile is=29.6 pounds.

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