RA Fisher is credited for numerous aspects of experimental design and modern statistical theory and practice. Some of his most important contributions include significance testing (Bandyopadhyay and Cherry 2011), maximum likelihood estimation (MLE), permutation (re-sampling) distributions, sufficiency, asymptotic optimality theory (Efron 1998), and experimental design components including randomization, replication, blocking, confounding, and the analysis of variance (ANOVA). Also of note is his contention of Mendel's Pea Plant experiment. He claimed it was "too good to be true."

Consider reading that Efron (1998) paper, "RA Fisher in the 21st century".

References
Bandyopadhyay, Prasanta S., and Steve Cherry. "Elementary probability and statistics: A primer." Philosophy of Statistics 7 (2011): 53.

Efron, Bradley. "RA Fisher in the 21st century." Statistical Science (1998): 95-114.

Sir Ronald Aylmer Fisher is credited for numerous aspects of experimental design and modern statistical theory and practice. Some of his most important contributions include significance testing (Bandyopadhyay and Cherry 2011), maximum likelihood estimation (MLE), permutation (re-sampling) distributions, sufficiency, asymptotic optimality theory (Efron 1998), and experimental design components including randomization, replication, blocking, confounding, and the analysis of variance (ANOVA). Also of note is his contention of Mendel's Pea Plant experiment. He claimed it was "too good to be true."

Consider reading that Efron (1998) paper, "RA Fisher in the 21st century". Let me quote the abstract:

Fisher is the single most important figure in 20th century statistics. This talk examines his influence on modern statistical thinking, trying to predict how Fisherian we can expect the 21st century to be. Fisher’s philosophy is characterized as a series of shrewd compromises between the Bayesian and frequentist viewpoints, augmented by some unique characteristics that are particularly useful in applied problems. Several current research topics are examined with an eye toward Fisherian influence, or the lack of it, and what this portends for future statistical developments. Based on the 1996 Fisher lecture, the article closely follows the text of that talk.

References

• Bandyopadhyay, Prasanta S., and Steve Cherry. "Elementary probability and statistics: A primer." Philosophy of Statistics 7 (2011): 53.

• Efron, Bradley. "R. A. Fisher in the 21st century." Statistical Science (1998): 95-114.