ABSTRACT
In the research of public programmes evaluation is heavily weighted with experimental or scientific connotations. Evaluators of public programmes are looking for methods which monitor the implementation of a programme or policy under experimental conditions. The purpose of evaluation research is to measure the effects of a programme against the goals it set out to accomplish as a means of contributing to the subsequent decision making about the programme and improving future programming. In medical research or psychological research the experimental/independent variable is a single stimulus - a drag/ treatment/ condition - a variable. In field experimentation concerning public policy the independent variable is a programme. Sesame Street formed one part of a public programme called 'Operation Head Start'. The strategy adopted to evaluate this programme was to target nursery classes in particular areas. As theory based evaluation has gained both credibility and use over time, confusion has also developed over understanding of the concept.
