The basic research question to be addressed in the present chapter is the following: How do we measure time-related change in a study with a non-experimental design? Or more specifically: How can we document possible effects of an intervention program against bully/victim problems in school when it is not possible to employ an experimental set-up with randomized assignment of observational units to various treatment conditions?

SOME BACKGROUND INFORMATION

Bully/victim problems among children (‘mobbing’) have been an issue of great concern in Scandinavia for almost two decades (Olweus, 1973, 1986, in preparation). There is a bully/victim problem in a class or a school when a student, repeatedly and over time, is exposed to harassment and attacks from one or several other students (Olweus, 1991). In addition, there should be a certain imbalance in the strength relations: the student who is exposed to the negative actions should have difficulty defending himself or herself and be somewhat helpless against those who harass.

In Norway, bully/victim problems were a matter of general interest and concern in the mass media and among teachers and parents for a number of years, but the school authorities did not engage themselves officially with the phenomenon. A few years ago, a marked change took place.