Which type of study is useful in quality assurance?

The necessity for studies in quality assurance is based on the demand for e valuation of quality assurance measures. Whereas investigation of effects o f quality assurance measures under controlled conditions is the goal of qua lity research, quality assurance deals with the improvement and assurance o f quality under routine conditions. In quality research a far reaching cont rol of bias and confounding variables should be aimed at. This is only poss ible with controlled studies, preferably with the randomised study. With me thodological demanding randomised studies the effectiveness of specific qua lity instruments (e.g. guidelines) could be demonstrated. In the evaluation of quality assurance comparison is also the major principle. This can be d one in a controlled non-randomised study, in an empirical comparison betwee n institutions or in a comparison with a given quality standard. It is hope d, that also in Germany methodological adequate studies will play a major r ole in quality research and quality assurance in the future.