ON THE DIFFERENCE BETWEEN STATISTICAL AND PRACTICAL SIGNIFICANCE IN SCHOOL-BASED DRUG-ABUSE PREVENTION

In recent years, a large number of research reports and review papers have claimed that effective school-based drug abuse prevention strateg ies have been developed and tested. 'Effectiveness' in these papers is generally assessed in terms of statistical significance. However, it cannot be assumed that a statistically significant difference observed at follow-tip between an intervention group and it control group is n ecessarily of any practical significance. Two large scale evaluations of school-based social influence programs are used to illustrate this point, and suggestions made as to how researchers might assess and rep ort on practical significance in future studies.