Saturday, April 22, 2017

Ronald Fisher: pioneer of modern statistics


Ronald Fisher (1890-1962) is a famous statistician best known for his contributions to statistics and evolution theory. Fisher has also been called the father of modern statistics. W. Allen Wallis says,
[Fisher] has made contributions to many areas of science; among them are agronomy, anthropology, astronomy, bacteriology, botany, economics, forestry, meteorology, psychology, public health, and-above all-genetics, in which he is recognized as one of the leaders. Out of this varied scientific research and his skill in mathematics, he has evolved systematic principles for the interpretation of empirical data; and he has founded a science of experimental design. On the foundations he has laid down, there has been erected a structure of statistical techniques that are used whenever people attempt to learn about nature from experiment and observation.
This post is a collection of quotes from Fisher describing his philosophy of statistics.

Analysis of data


"The analysis of variance is not a mathematical theorem, but rather a convenient method of arranging the arithmetic." (Quoted in Statistics in agricultural research by J. Wishart)

"However, perhaps the main point is that you are under no obligation to analyse variance into its parts if it does not come apart easily, and its unwillingness to do so naturally indicates that one’s line of approach is not very fruitful." (Letter to L. Hogben, 1933)

Significance testing


"The value for which P=0.05, or 1 in 20, is 1.96 or nearly 2; it is convenient to take this point as a limit in judging whether a deviation ought to be considered significant or not. Deviations exceeding twice the standard deviation are thus formally regarded as significant. Using this criterion we should be led to follow up a false indication only once in 22 trials, even if the statistics were the only guide available. Small effects will still escape notice if the data are insufficiently numerous to bring them out, but no lowering of the standard of significance would meet this difficulty.” (The Design of Experiments, 1935)

"Critical tests of this kind may be called tests of significance, and when such tests are available we may discover whether a second sample is or is not significantly different from the first." (Statistical Methods for Research Workers, 1925)

Hypothesis testing


"In relation to any experiment we may speak of this hypothesis as the 'null hypothesis', and it should be noted that the null hypothesis is never proved or established, but is possibly disproved, in the course of experimentation. Every experiment may be said to exist only in order to give the facts a chance of disproving the null hypothesis." (The Design of Experiments, 1935)

Critique of mathematics


"I believe that no one who is familiar, either with mathematical advances in other fields, or with the range of special biological conditions to be considered, would ever conceive that everything could be summed up in a single mathematical formula, however complex." (The evolutionary modification of genetic phenomena, 1932)

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