Design Facts at a Glance

Principal Investigator

J. Richard Udry
Kenan Professor of Maternal and Child Health and Sociology
Carolina Population Center
The University of North Carolina at Chapel Hill

Study Design

by J. Richard Udry, Peter S. Bearman, and Kathleen Mullan Harris
Special acknowledgment is due Ronald R. Rindfuss and Barbara Entwisle for assistance in the original design

Samples

Adolescent contexts studied

• individuals
• family
• friends and peers
• school
• neighborhood
• community

Young adult contexts studied

• same as above, with the addition of
• work force
• partners

Wave I, Stage 1

School sample: stratified, random sample of all high schools in the US. A school was eligible for the sample if it included an 11th grade and had a minimum enrollment of 30 students. A feeder school—a school that sent graduates to the high school and that included a 7th grade—was also recruited from the community.

High schools were stratified into 80 clusters

• Region—Northeast, Midwest, South, West
• Urbanicity—Urban, suburban, rural
• School size—125 or fewer, 126–350, 351–775, 776 or more students
• School type—public, private, parochial
• Percent white—0, 1–66, 67–93, 94–100
• Percent black—0, 1–6, 7–33, 34–100
• Grade span—K–12, 7–12, 9–12, 10–12
• Curriculum—general, vocational/technical, alternative, special education

Wave I, Stage 2

An in-home sample of 27,000 adolescents was drawn consisting of a core sample from each community plus selected special oversamples. Eligibility for oversamples was determined by an adolescent's responses on the In-School Questionnaire. Adolescents could qualify for more than one sample. In addition, parents were asked to complete a questionnaire about family and relationships.

Number of completed adolescent in-home interviews by sample

• Core—12,105 adolescents representative of adolescents in grades 7–12 during the 1994–1995 school year in the US
• Saturated schools—2,559 adolescents (in addition to the 200 students selected for the core) from schools in which all students were selected for in-home sample
• Disabled—471 adolescents who reported having a limb disability
• Blacks from well-educated families—1,038 black adolescents with a parent with a college degree
• Chinese—334 adolescents
• Cuban—450 adolescents
• Puerto Rican—437 adolescents
• Adolescents residing together Twin—1,981 adolescents
  Full sibling—1,186 adolescents
  Half sibling—783 adolescents
  Non-related adolescent—415 adolescents
  Sibling of twins—162 adolescents

Wave II

The Wave II in-home interview sample is the same as the Wave I in-home interview sample, with a few exceptions. In addition, school administrators were contacted by telephone to update school information. Information about neighborhoods/communities was gathered from a variety of previously published databases.

Wave III

The in-home Wave III sample consists of Wave I respondents who could be located and re-interviewed six years later. A sample of 1,507 partners of original respondents was also interviewed. Wave III also collected High School Transcript Release Forms as well as samples of urine and saliva.

Instruments

Wave I

• 90,118 adolescent In-School Questionnaires
  (September 1994–April 1995)
• 164 School Administrator Questionnaires
  (September 1994–April 1995)
• 20,745 adolescent In-Home Interviews
  (April 1995–December 1995)
• Add Health Picture Vocabulary Test
  (April 1995–December 1995)
• 17,700 Parent Questionnaires
  (April 1995–December 1995)

Wave II

• 128 School Administrator Questionnaires
  (May 1996–June 1996)
• 14,738 adolescent In-Home Interviews
  (April 1996–August 1996)

Wave III

• 15,197 young adult In-Home Interviews and biomarkers
  (July 2001–April 2002)
• Add Health Picture Vocabulary Test Scores
  (July 2001–April 2002)