The architecture of scientific research.

research question. On the basis of this question the researcher chooses the type of research that offers the best possibility of answering the research question. If the research question focuses on the onset or course of a disease, the best choice is an observational study design. If the research question focuses on the effectiveness of interventions, an experimental study design or, specifically, a randomised controlled trial is more appropriate. Critical consumers of scientific literature must determine whether the study design chosen is the best design with which to address the research question at issue. The conduct of scientific experiments symbolises what researchers do. In simple language the word 'experiment' refers to any type of research. For instance, the professional athlete experiments with various makes of sports shoes. However, scientific experiments have a number of specific characteristics which concern how systematic observations are made under controlled conditions. Many scientists stipulate one key characteristic of experiments: the research conditions are manipulated (Rothman and Greenland 1998). However, ethical considerations and practical problems often make scientific experimentation impossible. For example, it is not ethical to expose people to a risk factor just to be able to study how much influence this factor has on an illness. In many cases, such restrictions make it necessary for researchers to carry out non-experimental (observational) research. There are also methodological considerations which can influence the decision to conduct non-experimental studies. From this discussion it is clear that there is no rigid hierarchy in the 'strength' of the various study designs, even though a randomised controlled trial is often considered to be the 'strongest' design and case-control studies are often considered the 'weakest'. This simple hierarchy ignores the fact that the research question determines the choice of study design. The differences between experimental and non-experimental designs will be illustrated using examples of research on low back pain. Scientific research should always be based on a predetermined research question. The researchers then choose the type of research that offers the best possibility of answering the research question. Within the field of low back pain many research questions are still to be answered. For example, it is not yet known why some people who do not receive therapy recover from their back pain and some do not. We also still do not know which factors really induce low back pain, or which factors can prevent low back pain. There are also …