THE FUNDAMENTAL requirement for ethical treatment of research participants is that they give informed consent for their participation. Although there have been a few empirical studies of the consequences of informed consent (e.g., Singer, 1978), researchers need to know much more about the impact of this requirement on research results. This paper reports our findings regarding the consequences of obtaining written parental permission for research participation by minor students.Abstract The parents of an eligible sample of 1618 students in grades four through twelve were contacted to obtain written permission for their children to complete questionnaires related to alcohol and drugs. The distributions of students across the parental response categories (consent-denied, no-reply, or consent-granted) were compared on the student variables of sex, grade level, ethnic group, and reading and vocabulary test scores. The explicit consent procedure produced a sample that was approximately half the size of the eligible population and overrepresented white students while underrepresenting blacks and Asian Americans. There was no evidence of sample bias with respect to student gender, and the evidence regarding bias on academically related measures was mixed.

The success of a self-generated identification code for linking longitudinal questionnaire data was examined. The matching procedure developed for linking questionnaires, including a simple technique to compensate for nonidentical codes, yielded a high success rate (92% linkage of cases over a one-month interval and 78% over a one-year interval) and very few incorrectly linked cases. The procedure worked equally well with elementary and high school students, and the resulting samples were representative of the student population on a wide range of measures. Some suggestions are offered regarding the elements comprising self-generated codes.