Biostatistical approaches to reducing the number of animals used in biomedical research.

For ethical reasons, the least number of animals possible should be used in biomedical research, though not so few as to fail to detect biologically important effects or to necessitate the repetition of experiments. We describe biostatistical approaches that can contribute to either reducing the number of animals in single experiments or to increasing the quality of studies so that fewer subsequent studies (and thus animals) will be needed. The described approaches regard different phases of experimentation, specifically: planning the experimental design and calculating the sample size, controlling variability, choosing the response variable, postulating the statistical hypothesis to be tested, choosing the procedure for analysing data, and interpreting and suitably presenting the results.