Assessment of problems: which study design?

Evidence-based medicine has gained recognition in recent years, necessitating a large amount of conclusive results derived from a large number of experimental and epidemiological studies. Renal nurses are preferable investigators in this field because of their close relationship with the renal patient. Apart from clinical studies, with an experimental study design varying a single factor between two groups of patients, epidemiological studies are needed to assess actual problems. Epidemiological studies are purely based on observation, without altering any factor. The choice of study design will depend on the available knowledge about the problem and available resources.