NCJ Number
130395
Date Published
1990
Length
35 pages
Annotation
This study assesses the impact of baseline nonresponse in Project ALERT (Adolescent Experiences in Resistance Training), a longitudinal experiment that tests the effectiveness of a school-based drug prevention program for 7th- and 8th-grade students in 20 treatment and 10 control schools in California and Oregon.
Abstract
This analysis examines how many students were lost because of baseline nonresponse, how each group of nonrespondents (parent refusals, student refusals, and absentees) differed from respondents, how nonresponse changed the sample, and whether nonresponse introduced differences among the treatment groups. To evaluate the programs' effectiveness, researchers asked students to complete questionnaires about their drug use and related topics and to provide saliva samples. To reduce the impact of baseline nonresponse, passive informed consent was used; this required a parent to return a consent form only if permission was denied. Absentees were recaptured in 18 schools by using makeup data-collection sessions. Some 8.5 percent of parents denied consent, which accounted for the majority of baseline nonresponse. Slightly less than 1 percent of students refused to fill out a questionnaire or provide a saliva sample. The steps taken to reduce baseline nonresponse -- passive informed consent, careful explanation of data privacy, and makeup sessions for absentees -- proved effective. They held the combined level of baseline nonresponse to 16 percent. The steps significantly limited differences between the baseline population and baseline sample and avoided substantial differences among the treatment groups. 6 tables, 2 figures, and 16 references