The NCS-A is a nationally representative, face-to-face survey of 10,123 adolescents aged 13–18 years in the continental US.17 The survey was administered by the professional interview staff of the Institute for Social Research at the University of Michigan. The NCS-A was carried out in a dual-frame sample that included a household sub-sample and a school sub-sample.18, 20, 21 The overall NCS-A adolescent response rate combining the two sub-samples was 82.9%. Comparisons of sample and population distributions on census sociodemographic variables and the school sample on school characteristics revealed only minor differences that were corrected with post-stratification weighting.
