ADMINISTRATION MODE BIAS IN A SCHOOL SURVEY ON ALCOHOL, TOBACCO AND ILLICIT DRUG-USE

School surveys have become the most common method for determining the general level of tobacco, alcohol and illicit drug use among adolescen ts in a large number of countries. The two most commonly applied field procedures in school surveys are teachers' and researchers' administr ation of questionnaires. The impact of the difference between these tw o modes of administration has not been determined, although it has bee n argued that central involvement of teachers in data collection may d ecrease the perceived anonymity of the survey among students, and shou ld thus be avoided. In a split-half random sample of 3017 urban, Icela ndic 16-20-year-old students, no statistically significant differences were found in reported use of licit or illicit drugs, nor in the stat ed willingness to be honest between these two modes of administration. These results suggest that when students return their responses in se aled envelopes, the two modes of administration produce equally valid results.