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Technical Notes

Child Health Assessment and Monitoring Program (CHAMP)

Interpreting Results Tables

Detailed data tables for N.C. CHAMP survey items are posted on a bi-annual basis. Exact wording for each question is used as a title for most survey items; however, due to space limitations, titles may not include some introductory remarks and explanations for some questions. For further information on survey questions, refer to the corresponding annual questionnaire available at the Questionnaires section of this site.

State level estimates are available for survey items tabulated by characteristics of the child, including sex, race, Hispanic origin, age group, school enrollment type (public/private), grade level, health insurance status and Special Health Care Needs status, as well as parental education level. County-level estimates are not reported due to relatively small sample sizes.

Percentages shown in N.C. CHAMP data tables are calculated using weighted data and therefore cannot be derived exactly from the numbers in the tables. Weighting adjusts for unequal probabilities of selection due to the disproportionate sampling method and due to people living in households with different numbers of telephones and different numbers of children. Data are also weighted to account for unequal non-response rates among different demographic groups. For example, if parents of children under five constitute 10 percent of the sample respondents, but this group represents 8 percent of the total population of the state, then a factor of 0.80 would be entered into the last weighting process for these respondents to account for this discrepancy. Thus, the weighting procedure adjusts the results of the sample to better represent the entire population of children in North Carolina. For further information, refer to the Design and Data Collection documentation section of this site.

N.C. CHAMP data tables present the 95 percent confidence interval (C.I.) associated with each estimate, or percent, reported in the tables. Given the complex sample design of the N.C. CHAMP Survey (i.e. it is not a simple random sample), the State Center for Health Statistics uses SUDAAN software to calculate the point estimates and confidence intervals. This software takes into account the complex sampling design, when computing the variance, or sampling error, associated with the estimates. The 95 percent confidence interval indicates the range in which the true population value would occur 95 out of 100 times, if 100 different random samples were taken of the population.

For several years the CDC BRFSS program has suppressed prevalence estimates which did not meet minimal criteria for statistical reliability based on sample size and the width of the confidence intervals. To better meet our goal of providing high quality health information for better informed decisions and effective health policies, the SCHS has adopted this practice for our CHAMP web tables.

We suppress prevalence estimates when any of the following criteria are met:

  1. There are fewer than 10 respondents in the numerator (i.e. the number of respondents associated with the response categories, e.g. “Yes-No”).
  2. There are fewer than 50 respondents in the denominator (i.e. the total number of respondents to a question).
  3. The width of the confidence interval for the prevalence estimate is greater than 20.
  4. Cases where a table cell estimate has a relative standard error of greater than 30 percent. The relative standard error is a measure of a statistical estimate's reliability obtained by dividing the standard error by the estimate; then multiplied by 100 to be expressed as a percentage.

Respondents who refused to answer or did not know the answer to a survey question were excluded from calculations in the data tables. However, for a few questions "Don't know/Not sure" responses provide valuable information and were included in the calculations. The denominator for each calculation is the number of participants who responded to the item. Exceptions are specified in the footnote of the corresponding data table.