Students must be encouraged to undertake a critical evaluation of the work they have does. In this analysis, the student should describe and explain the limitations imposed on the research by factors such as the suitability and reliability of the sources accessed, accuracy and precision of measuring equipment, sample size, validity and reliability of statistics. Biological limitations should be considered, such as those arising from the problem of repeatability and control when using living material, as the well as the difficulties of generalizing from research based on a single type of organism or environment.