[Evaluation of effectiveness of interventions in public health (author's transl)].

The concepts of effect and effectiveness are summarized within the framework of evaluation of public health interventions. Effect is defined as a modification of the level and structure of health problems and of the demand of health care, resulting from health and health-related activities. The concept of effectiveness is complex: in a qualitative sense, it is the property of producing an effect; in a quantitative sense, the effectiveness of a technique is the relationship between the effect of that technique and the initial magnitude of the relevant problem. The quantitative effect of a public health programme is determined by the effectiveness of the technique as applied in the field, the magnitude of the problem and the coverage attained. It is only the comparison between randomized groups that can prove the existence of non-existence of an effect; nevertheless, other less demanding types of studies can be useful for monitoring progress at the national level. Examples of each category of evaluation are presented.