Prediction: Encyclopedia II - Prediction - Scientific prediction

Prediction - Scientific prediction

In a scientific context, a prediction is a rigorous (often quantitative) statement about what will happen under specific conditions, typically expressed in the form If A is true, then B will also be true. The scientific method is built on testing predictions which are logical consequences of scientific theories. A scientific theory whose predictions are not in accordance with observations will probably be rejected. Additionally, if new theories generate many new predictions, they are often highly valued, for they can be quickly and easily confirmed or falsified (see predictive power). In many scientific fields, desirable theories are those which predict a large number of events from relatively few underlying principles.

In microprocessors, branch prediction permits to avoid pipeline emptying at microcode branchings.

Prediction - Example

In the 1840s the renowned Austro-Hungarian physician Ignaz Semmelweis noticed that women giving birth in the Vienna lying-in hospital were dying in one building, but surviving in another.

Upon considering the cause, he found that the surviving women were attended by midwives and not by student physicians. Thus he proposed the hypothesis that the physicians were a factor in the deaths.

This proposition impelled Semmelweis to refine the factor. What was the difference between the midwives and the doctors? After more thought, Semmelweis decided that the cadavers which the student doctors were touching must be part of the factor.

What could the doctors do to avoid the factor? Semmelweis predicted that, if the doctors were to wash their hands, then the cadaver factor will be avoided.

Semmelweis therefore instructed the student doctors to wash their hands, and the women who were attended by the doctors survived. Thus his prediction was successful, and his explanation was validated.

(Semmelweis, 1861. The Etiology, Understanding, and Prophylaxis of Childbed Fever)

Other examples abound in the history of science, ranging from expected predictions which did not occur (such as the Michelson-Morley experiment) to new and radical predictions which shockingly confirmed one theory over another (such as the bending of light around the sun seen in the 1919 eclipse, a prediction of Albert Einstein's theory of General relativity).

Adapted from the Wikipedia article "Scientific prediction", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki