Reference Population Expected Rates: CDC Growth Charts

Reference Population Expected Rates: CDC Growth Charts
The reference population used to construct the CDC Growth Charts is a nationally representative sample obtained from five national health examination surveys conducted by National Center for Health Statistics (NCHS) from 1963 to 1994. In the reference population approximately 5 percent of children are expected to fall below the 5th
percentile for both short stature and underweight due to normal biologic variation. Therefore, the expected rate in the population for both of these indicators is 5 percent.

Likewise, for overweight children, 10 percent are expected to fall between the 85th and 95th percentiles and for overweight 5 percent of children are expected to be above the 95th percentile due to normal biologic variation. Prevalence of a health indicator greater than the rate expected in a population based on reference data indicate that the population has a higher proportion of individuals with a given health indicator than would be expected based on the reference population. For example, if the prevalence of overweight in national PedNSS data is 12 percent, it is more than two times the expected rate of 5 percent, and, therefore, a health problem in this population.