Fisher, Ronald Aylmer (1890-1962) was a British statistician and geneticist whose ideas laid the foundation for the field of modern statistics. His contributions to the field of genetics, particularly those related to evolution and biometrics, were also outstanding.

Fisher was born in London and was a student at a time when Charles Robert Darwin 's theories were still a subject of major scientific controversy. At the time, Gregor Johann Mendel 's work on genetics was being rediscovered, and Mendel's ideas greatly interested Fisher.

After graduating from Cambridge University in 1912, Fisher worked as a statistician at an investment company. In 1919, he joined the statistical department at Rothamsted Experimental Station, an agricultural research station. There he carried out statistical experimentation with plant breeding, which led to a technique for varying different factors in an experiment and determining the probability of these factors causing different experimental results. This technique, called variance analysis, was a significant step beyond the prevailing practice of the day, which was to vary only one factor at a time in an experiment. Variance analysis was especially significant, because it solved similar problems of statistical analysis in other branches of science as well.

Fisher developed theories about gene dominance and fitness and did research to develop methods of analysis related to the linkage of genes for different traits. He also introduced the principle of randomization. Essentially, this principle applies experimental procedures to randomly selected samples from the experimental group. Random selection is used to diminish the effects of variables in the group, so that the results of the experiment apply reliably to the group as a whole.

Fisher developed many of the specific aspects of both theoretical and applied statistics. His work is considered the basis of modern mathematical statistics.

Fisher was knighted in 1952 and later moved to Australia, where he lived and conducted research until his death.