It is the researcher's plan for testing the validity of a hypothesis. Much thought and hard work accompany the development of a hypothesis and experiments that will yield clear results. A scientist's ability to ask key questions and to formulate them into testable hypotheses may largely determine the success or failure of a given research project. The very nature of some questions requires estimations or assumptions to be made. Whenever estimations or assumptions are part of the experimental design, they must be clearly stated and justified as part of the experiment.
Any estimation is based on some type of data.
The data must be shown as well as the calculations that lead to the final estimate. An assumption is based on some fact. Any assumptions that are key to the experimental design must be stated as well as the reason for starting with this assumption. A control group receives the same treatment as the experimental group except that the factor being tested is applied to the experimental group only, not to the control. Second , experiments must be repeated enough times to allow comparisons between experimental and control groups.