To define sufficient subjects.
The problem of how many subjects are required for a particular investigation can be solved. Techniques developed to allow experimenters to determine the statistical power of their experiments can be adapted to this end provided that the investigator is prepared to define the significance level and, more importantly, the minimum strength of experimental effect that is of interest. The experience described in this article demonstrates that the process demands consideration of a number of factors like the nature of the dependent variable, the form of the decision being made, and the minimum difference between conditions which has practical consequence.
D002986:Clinical Trials as Topic / Q000379:methods*; D006801:Humans; D012107:Research Design; D013223:Statistics as Topic