Experimental studies seek to verify the truth (accuracy corresponding to reality) or falsity (inaccuracy) of a hypothesis, which is a proposed explanation for some phenomena that can be tested by manipulating an independent variable and observing the effects on a dependent variable. Normative studies seek to clearly define the study population, outline the hypothesis under research, use scientific method to gather relevant data and appropriately interpret the results. Survey method seeks to test a hypotheses about aspects/characteristics/nature/attitude of relationships within a population.by questioning individuals and describing their responses. Historical studies use primary sources and other evidence, including the evidence of archaeology, to research and write accounts of the past. No hypothesis is required in this method.