Methods


Shortcuts to sections of the Methods
BD14752_.GIF (667 bytes) Background
BD14752_.GIF (667 bytes) Methods
  BD14752_.GIF (667 bytes) Description of the Survey
  BD14752_.GIF (667 bytes) Description of the Sample Selection Process
  BD14752_.GIF (667 bytes) Description of Survey Administration in Classrooms and Strategies to Ensure the Privacy of Responses
  BD14752_.GIF (667 bytes) Description of Sample, Response Rate, and Weighting
BD14752_.GIF (667 bytes) 2003 Middle School Sample
BD14752_.GIF (667 bytes) 2003 High School Sample



Background
The first representative Youth Risk Behavior Surveillance System (YRBSS) survey data collection was in 1997 when seven middle schools in Shiprock Service Unit and most public high schools located on or near the Navajo Nation participated. In 2000 and in 2003, the survey was administered at most middle and high schools located on or near the Navajo Nation. Previously, the Bureau of Indian Affairs funded schools were not included, but they participated in the 2003 Navajo YRBS.

Methods

Description of the Survey
The YRBSS survey uses a questionnaire to assess the prevalence of risk behavior that contribute substantially to the leading causes of death, illness, and social problems among youth and adults in the United States. The survey monitors six categories of priority risk behaviors that contribute to unintentional injuries and violence, tobacco use, alcohol and other drug use, sexual behaviors that contribute to unintended pregnancy and sexually transmitted diseases (STDs), including human immunodeficiency virus (HIV) infection; unhealthy dietary behaviors; and physical inactivity plus overweight. The 80 item New Mexico middle school instrument that contained some protective factor questions was used for the middle schools survey, and the 87 item CDC high school instrument was administered in the high schools.

Description of the Sample Selection Process

The schools targeted for participation were those located on the Navajo Nation reservation or in bordering towns with at least 50% Navajo student enrollment; this included 86 middle schools and 44 high schools. After the school provided the number of enrollment, a detemination was made to administer the survey to all students at smaller schools and to administer the survey in randomly selected classrooms in larger schools. The survey was given during the second hour (period) to capture the most students. In schools that participated, the middle school questionnaire was administered to grades 6, 7, and 8, and the high schools questionnaire was administered to grades 9, 10, 11, and 12.

Description of Survey Administration in Classrooms and Strategies to Ensure the Privacy of Responses

During the spring 2003, all students in selected classrooms, were asked to participate at participating schools. Packets containing instructions and the questionnaires were provided for teachers and volunteers to administer the survey. The survey procedures were shared with the students. To protect students' privacy the students were assured that their participation was voluntary and they they would remain anonymous. To protect students' privacy, they were told not to record their name, student identification number, or any other information that could identify them individually. Students recorded their answers directly on a scannable form or booklet.

Description of Sample, Response Rate, and Weighting

After the middle school forms were scanned at Shiprock Service Unit, the data along with the high school forms were sent to Westat for data processing. The following procedures were used to determine the 2003 response rate and weighting.



2003 Middle School Sample

School Level - All schools containing grades 6, 7, and 8 were asked to participate. Forty-six of these schools were also BIA schools.
Class Level - All classes in a required subject or all classes meeting during a particular period of the day, depending on the school, were included in the sampling frame. Systematic equal probability sampling with a random start was used to select classes from each school that participated in the survey.
2003 Response Rate
  School response rate: 86%, 74 of the 86 eligible schools participated.
  Student response rate: 71%, 8,493 of the 11,971 sampled students completed usable questionnaires.
  Overall response rate: 61% = 86% * 71%
Weighting
A weight has been associated with each student record to reflect the likelihood of sampling each student and to reduce bias by compensating for differing patterns of nonresponse. The weight used for estimation is given by:
    W = W1 *f1 * f2 * f3
  W1 = The inverse of the probability of selecting the classroom within the school
    f1 = A school-level nonresponse adjustment factor calculated by school size category (small, medium, large). The factor was calculated in terms of school enrollment instead of number of schools.
  f2 = A student-level nonresponse adjustment factor.
  f3 = A poststratification adjustment factor calculated by gender within grade.
Use of the Weighted Results
The weighted results can be used to make important inferences concerning the priority health-risk behaviors of all school students in grades 6 through 8.


2003 High School Sample

School Level - All schools containing grades 9, 10, 11, and 12 were included in the sample. Fifteen of these schools are also BIA schools.
Class Level - All classes in a required subject or all classes meeting during a particular period of the day, depending on the school, were included in the sampling frame. Systematic equal probability sampling with a random start was used to select classes from each school that participated in the survey.
2003 Response Rate
  Schools:- 80%, 35 of the 44 eligible schools participated.
  Students: 67%, 8,374 of the 12,545 sampled students completed usable questionnaires.
  Overall response rate: 53% = 80% * 67%
Weighting
In probability sampling, associating a weight with each student record is intended to reflect the likelihood of sampling each student and to reduce bias by compensating for differing patterns of nonresponse. The low overall response rate precludes weighting of the data.
Use of the Unweighted Results
The unweighted results provide a description of the priority health-risk behaviors of the survey participants. These results cannot be generalized to other students.