Sunday, April 24, 2016

Sir Ronald Aylmer Fisher

Sir Ronald Aylmer Fisher (1880-1962) is a sublime candidate for a mathematician who developed statistical means to test the validity of scientific research happening in the scientific community around him. Luckily, Fisher being active in London in the early 20th century, he was surrounded by the relatively recent work of prominent names in evolutionary biology and statistics such as Charles Darwin, Gregor Mendel.

Though Fisher studied Astronomy at the University of Cambridge, he had a deep interest in evolutionary theory. In 1918, he published a paper title The Correlation of Relatives on the Supposition of Mendelian Inheritance that bridged the inconsistencies between the works of Mendel and Darwin. It is often thought that if Darwin and Mendel had not been so isolated from each other's’ work during their lives, the field of evolutionary biology would have developed very differently. Fisher was aware of both of their work, and his paper caught the attention of renowned statistician Karl Pearson, who offered him a spot in his laboratory at University College London.

Instead, Fisher chose to take up a position at the Rothamsted Experimental Station, which today is the world’s oldest agricultural research station. This turned out to be a favorable step in Fisher’s career as a statistician, because at Rothamsted, he was given access to incredibly large databases of plant breeding experiments dating back decades. Not only did he have access to past experiments, Fisher was able to design his own studies, and be part of the statistical process in planning and setting up an experiment from the very beginning. In 1925, Fisher published Statistical Methods for Research Workers, which remained in print for over 50 years, serving as a guidebook for statistics for scientists around the world.

In fact, when Fisher did go to University College London, he returned not as just a statistician, but as a professor. He would then go back to Cambridge in 1943 as the Balfour Professor of Genetics, where he continued working until 1957. During his time at Cambridge, Fisher published Statistical Methods and Scientific Inference, a publication that still serves as a landmark in the history of statistics as a collection of all the important achievements of Fisher’s career as a statistician, and was knighted by Queen Elizabeth II for his contributions to science and society.

The legacy left behind by Fisher is a tall order to list briefly. He was the first to introduce the concept of randomization during experimental setup. Aware of the biases that occurred during scientific research, Fisher emphasized the role of randomizations and controls in ensuring the validity of an experimental finding. Fisher’s earliest work developed the idea of maximum likelihood, the method for estimating the parameters of a statistical model given a dataset, the popularization of which Fisher was responsible for. He coined the term ‘Null hypothesis’ and even set the convention of the arbitrary p value to 0.05 to determine statistical significance. Perhaps one of his most prominent achievements was the development of analysis of variance, or the ANOVA test.

Fisher is known for several other contributions, including Fisher’s principle, the model explaining the uniformity of the male/female ratio in sexually reproducing populations. He explained the Fisherian Runaway, the model of evolution that outlines female preferences for highly ornamented males and the Sexy Son Hypothesis, the model of evolution that females select mates based on the mate’s ability to produce sexually attractive offspring, not the male’s ability to provide or nurture. Fisher is even considered by some to be one of the founders of population genetics, as he spent the majority of his career studying the distribution and frequency of alleles within a population along with factors of adaptation, speciation, and population structure.

Even with such a resume, Fisher was not completely free of biases. He never agreed to the association between tobacco and lung cancer, as was shown in the mid-20th century. Though it is somewhat comical that some think he accepted funds from the tobacco firms for his opinion on that work.

After his time at Cambridge, Fisher moved to Australia, where he continued to conduct research until his death in 1962. He was a statistician with impeccable contributions to his field and immaculate skill in mathematics to execute his ideas, which will continue to always play a central role in how statistics is done by scientists.

1 comment:

  1. Interesting to know that R.A. Fisher set the conventional p value to determine statistical significance. How much different would our methods of doing science and wholescale familiarity with statistics be as a community if another threshold had been chosen? According to this Vox article on "P value obsession" (, Fisher intended the P value to be used as part of the statistical toolset for examining experimental data. Maybe if he had chosen a different threshold (say 0.10?) that was less stringent, the p value wouldn't be treated like a bellwether for the importance of a finding.