How To Design Research Experiments..
Scientists test their hypotheses by designing and running experiments. A well-designed experiment involves two groups of people or objects. The scientists change one element, called a control variable, and record how that changes the outcome of the experiment. For example, suppose a scientist wants to find out whether adding salt to water changes the water's boiling point. The scientist would have to boil exactly the same amount of water, use pots made out of the same material, use the same equipment to boil the water, and so forth. Ideally, the only thing that would be different would be the addition of salt, or not, into the water.