Why is it important for the experimental results of one scientist to be tested by another scientist?
Scientists test hypotheses through experimentation. The inquiry usually begins with an idea that the scientist has, based on her observations. For example, she could notice that the silver paint on her old automobile has faded, discolored and peeled, whereas the red paint on similar vehicles has not. Her theory might be that silver paint, when exposed to the elements, undergoes a higher rate of degradation than does red paint. To test this theory the scientist could paint sheets of metal with the two colors, expose them to the elements over time, and observe and record the results. This process would constitute a scientific experiment.
Scientific experiments must be controlled and reproducible. This means that variables that could affect the outcome other than those being measured must be controlled. In this experiment, for example, one would have to control the variable of metal surface type. She would have to ensure that both paint colors were painted on exactly the same shape and type of metal. Similarly she would have to control the degree of exposure to the elements of both samples, making sure both color samples were exposed to the same intensity and duration of sunlight.
By “reproducible” is meant that another scientist can duplicate the experimental results. The experiment must be described in sufficient detail in the scientific literature for another scientist to reproduce the experiment and, we hope, confirm the results.
These and other features, which define proper and valid modern scientific inquiry, are found under the heading of “The Scientific Method” (see reference).