Reproducibility

Reproducibility is one of the main principles of the scientific method, and refers to the ability of a test or experiment to be accurately reproduced, or replicated. The term is closely related to the concept of testability. A related concept is the need for measured parameters to have an operational definition, that is, that the parameter or component of a theory have a defined procedure for its measurement.

Reproducibility of experimental data is not an absolute scientific requirement in all of sciences; some fields, such as history and astronomy, rely in part upon the observation of singular phenomena. It is also the case that some phenomena are so unusual that an experiment is practically not reproducible, for example we can not take probes frequently from Comet Halley. However, in most of natural sciences we expect experiments to be designed in a way that makes them potentially independently reproducable.

Whether a given experiment is in fact replicated independently largely depends on whether the outcome of the experiment was predictable or unexpected, and on whether the results have potentially important implications. Direct exact replication of an experiment is something quite unusual, and indeed it is generally difficult to publish results that are mere confirmations of previous work. In general, scientists will prefer to repeat the test but by independent scientific means, on the grounds that if two different, complementary lines of evidence both come to the same, unexpected conclusion, an artefactual explanation for the unexpected result is less likely. Thus direct replication of an original experiment is something that usually takes place only when the validity of the original result is explicitly challenged.

Reproducibility is also the variation in measurements taken by different persons or instruments on the same item and under the same conditions.

Famous problems

In the late 1980's there was a rush to publish on the subject of cold fusion, a technology that offered promise of low-cost energy. In March 1989, University of Utah chemists Stanley Pons and Martin Fleischmann reported the production of excess heat that could only be explained by a nuclear process. The report was astounding given the simplicity of the equipment: it was essentially an electrolysis cell containing heavy water and a palladium cathode which rapidly absorbed the deuterium produced during electrolysis. The newsmedia reported on the experiments widely, and it was a front-page item on many newspapers around the world. Over the next several months others tried to replicate the experiment, but were unsuccessful. At the end of May the US Energy Research Advisory Board formed a special panel to investigate cold fusion. The scientists in the panel found the evidence to be unconvincing. Pons and Fleischmann later apparently claimed that there was a "secret" to the experiment, a statement that infuriated the majority of scientists to the point of dismissing the experiment out of hand. The science of cold fusion was severely damaged by the affair, although research continues quietly around the world.

See also

Pseudoscience Scientific method

References

• Turner, William (1903), History of Philosophy, Ginn and Company, Boston, MA, Etext. See especially: "Aristotle".

• Definition (PDF)

External links

• Guidelines for evaluating and expressing the uncertainty of NIST measurement results; appendix D
• Definition of reproducibility in the IUPAC Gold Book
• Article on Reproducibility