Chapter 17, Problem 54E

Exercises 53 through 56 refer to the distribution of weights for infants by age and gender. In all cases you can assume that the weight distribution is approximately normal. The data for these exercises are taken from the 2000 clinical growth charts by the Centers of Disease Control and Prevention (CDC) (www.cdc.gov/growthcharts/clinical_charts.htm).

The distribution of weights for six-month-old baby girls has mean $\mu =9.7\text{ kg}$ and standard deviation $\sigma =1.0\text{ kg}$.

a. Suppose that a 12-month-old girl weighs 7.7 kg.

Approximately what weight percentile is she in?

b. Suppose that a 12-month-old girl weighs 10.4 kg.

Approximately what weight percentile is she in?

c. Suppose that a 12-month-old girl is in the ${84}^{th}$ percentile in weight. Estimate her weight.