Survey Methods

The NS-CSHCN was fielded using the State and Local Area Integrated Telephone Survey (SLAITS) mechanism. SLAITS is conducted by the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention (CDC). It uses the same large-scale random-digit-dial sampling frame as the CDC’s National Immunization Survey.1

Over 7 million telephone numbers were randomly generated for inclusion in the NS-CSHCN. Separate random-digit-dial samples were generated for landline and cellphone numbers. After eliminating numbers that were determined to be nonresidential or nonworking, the remaining numbers were called to identify households with children under 18 years of age. In addition, when cell phones were called, respondents were considered eligible only if they reported that they did not have a landline telephone or if they said they were unlikely to be reached through a landline. When households with children were identified, all children in the household were screened for special health care needs. In households where two or more children were identified as having special needs, one child was randomly sampled to be the subject of the detailed interview.

The goal was to complete approximately 750 interviews regarding a sampled child with special health care needs in each of the 50 States and the District of Columbia. The number of households screened in each State in order to identify these 750 CSHCN varied depending on the prevalence of CSHCN in each State.

Questionnaire

CSHCN were identified using the CSHCN Screener, which consists of five questions concerning common health care consequences of a chronic condition experienced by CSHCN. The questionnaire for sampled CSHCN included sections regarding health and functional status, access to care, care coordination, satisfaction with care, health insurance coverage, adequacy of health care coverage, impact of the child’s special needs on the family, and demographic information about the child, respondent, and household.

The respondent was the parent or guardian in the household who was knowledgeable about the health and health care of the children under 18 years of age. For 75 percent of the children, the respondent was the mother. Respondents for the remaining children were fathers (17 percent), grandparents (6 percent), or other relatives or guardians (2 percent).

Data Collection

Data collection began on July 7, 2009 and ended on March 2, 2011, with interviews conducted from telephone centers in Chicago, Illinois, and Las Vegas, Nevada. A computer-assisted telephone interviewing system was used to collect the data. From 196,159 households with children, 372,698 children were screened for special health care needs and 40,242 interviews were completed regarding CSHCN. Of the total number of completed interviews, 2,991 were conducted within the cell-phone sample. The special-needs interview completion rate, which is the proportion of interviews completed after a child with special needs was selected in the household, was 83.6 percent for the landline sample, 76.6 percent for the cell-phone sample, and 80.8 percent for the combined sample. Combined interview completion rates ranged from 73.9 percent in Hawaii to 86.2 percent in Vermont. The national weighted response rate, which includes the cooperation rate as well as the resolution rate (the proportion of telephone numbers identified as residential or nonresidential) and the screening completion rates (the proportion of households successfully screened for children and for CSHCN), was 43.7 percent for the landline sample, 15.2 percent for the cellphone sample, and 25.5 percent overall.

Data Analysis

For producing the population-based estimates in this report, the data records for each screening interview and for each special needs interview were assigned a sampling weight. These weights are based on the probability of selection of each household telephone number within each State, with adjustments that compensate for households that have multiple telephone numbers, for households without telephones, and for non-response. With data from the U.S. Bureau of the Census, the weights were also adjusted by age, sex, race, ethnicity, income, highest level of education among adults in the household, and household size to provide a dataset that was more representative of each State’s population of children less than 18 years of age. Analyses were conducted using statistical software that accounts for the weights and the complex survey design. Responses of “don’t know” and “refuse to answer” were counted as missing data.

Accuracy of the Results

The data from the NS-CSHCN are subject to the usual variability associated with sample surveys. Small differences between survey estimates may be due to random survey error and not to true differences among children or across States.

The precision of the survey estimates is based on the sample size and the measure of interest. Estimates at the national level will be more precise than estimates at the State level. Estimates of the prevalence of special health care needs among all children will be more precise than estimates of the health and health care of CSHCN. The margin of error for the national prevalence estimate is 0.2 percentage points. For national estimates of the health and health care for all CSHCN, the maximum margin of error is 1.4 percentage points. For State prevalence estimates, the maximum margin of error is 2.1 percentage points. For the State indicators, the maximum margin of error is 11.8 percentage points, though half of the State indicators have a margin of error less than 7.3 percentage points.

Except for data suppressed to protect the confidentiality of the survey subjects, all data collected in the NS-CSHCN are available to the public on the NCHS and MCHB Web sites.

For children in racial groups that do not represent at least 5 percent of the population in a State, the child’s race was coded as “other.” In other cases, information on the child’s race is included in the data set but not reported in this chartbook. Because the number of interviewed children in a racial group was small, the relative standard error of the estimate was greater than 30 percent. Estimates with relative standard errors greater than 30 percent are not considered reliable or precise. Data documentation and additional details on the methodology are also available online.

1 Zell ER, Ezzati-Rice, TM, Battaglia MP, Wright RA. National Immunization Survey: The Methodology of a Vaccination Surveillance System. Public Health Reports 115:65-77, 2000. Return to text.

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