Why Should Experiments Be Repeated?

Verification and Reliability

• For a theory to be useful in the scientific method, it must be both reliable and valid. Reliability refers to the consistency with which an experiment gives the same results when repeated. Validity refers to the degree to which those results conform to reality. Repeating an experiment makes it easier to see whether it's reliable because there are more data points to compare. An unreliable experiment may seem reliable if it happens to give consistent results the first two or three times, but with further repetition, its unreliability will become evident.

Independent Testing

• Communication and peer review are very important to the scientific progress because they allow scientists in different settings to perform the same experiments and confirm or dispute the original results. It's always possible that the scientist performing an experiment will have unknown biases or neglect certain significant factors. If that scientist is the only one to ever perform the experiment, the resulting errors could go undiscovered. When other scientists successfully repeat the experiment, however, it can help confirm the results and strengthen the resulting theory.

Refining Results

• While it's often worthwhile to repeat an experiment using an identical method, in some cases, scientists also seek to modify aspects of the original experiment to gain further insight. Repeating an experiment with a new adjustment to the method can take into account of variables that the original experiment neglected, modify the process under investigation, or otherwise provide the opportunity for new understanding resulting in a richer model than was possible using only the information from the experiment's original form.

Increase Yield

• There may be more direct reasons to repeat experiments used to synthesize or extract a useful substance. Performing the same experiment again yields more of the product, such as a chemical compound with medicinal properties or a bacterial culture worth studying. In the process of repeating and refining these experiments, scientists may also be seeking more efficient ways to produce or extract the substance, or ways to alter the method to create an even more useful form of it.