Before the beginning of this century, statistics meant observed data and descriptive summary figures, such as means, variances, indices, etc., computed from data. With the introduction of the $\chi^2$ test for goodness of fit (specification) by Karl Pearson (1900) and the $t$ test by Gosset (Student, 1908) for drawing inference on the mean of a normal population, statistics started acquiring new meaning as a method of processing data to determine the amount of uncertainty in various generalizations we may make from observed data (sample) to the source of the data (population). The major steps that led to the establishment and recognition of statistics as a separate scientific discipline and an inevitable tool in improving natural knowledge were made by R. A. Fisher during the decade 1915-1925. Most of the concepts and methods introduced by Fisher are fundamental and continue to provide the framework for the discussion of statistical theory. Fisher's work is monumental, both in richness and variety of ideas, and provided the inspiration for phenomenal developments in statistical methodology for applications in all areas of human endeavor during the last 75 years. Some of Fisher's pioneering works have raised bitter controversies that still continue. These controversies have indeed helped in highlighting the intrinsic difficulties in inductive reasoning and seeking refinements in statistical methodology.
"R. A. Fisher: The Founder of Modern Statistics." Statist. Sci. 7 (1) 34 - 48, February, 1992. https://doi.org/10.1214/ss/1177011442