Jacob Cohen

Jacob Cohen (April 20, 1923 – January 20, 1998) was an American psychologist and statistician.^[1] He is best known for his work on statistical power and effect size. His research helped develop modern statistical methods and meta-analysis. Several statistical measures are named after him, including Cohen’s kappa, Cohen’s d, and Cohen’s h.^[2][3]

Cohen was born in New York City, United States, on April 20, 1923. He grew up in a family that spoke Yiddish at home and learned English at school. He attended Townsend Harris High School and graduated when he was 15 years old.

He studied at the City College of New York. At first, he studied mathematics, but his education was interrupted when he served in the United States Army Intelligence during World War II. After the war, he returned to college and earned a bachelor’s degree in psychology in 1947.

Cohen later studied at New York University (NYU), where he received a master’s degree in 1948 and a PhD in clinical psychology in 1950. His doctoral advisor was Avrum Ben-Avi.^[4]

Cohen is famous for his work on statistical power analysis and effect size. He encouraged researchers to look beyond simple significance tests and to pay more attention to the size and practical importance of results.^[2][3]

He also criticized common misunderstandings about statistical significance and argued that scientific findings should be supported through replication rather than by a single study.

Cohen developed guidelines for interpreting statistical measures such as the correlation coefficient (r) and the standardized mean difference (d).^[5]

Cohen was president of the Society of Multivariate Experimental Psychology in 1969.

He received the Distinguished Lifetime Achievement Award from the American Psychological Association in 1997. He was also a fellow of the American Association for the Advancement of Science, the American Psychological Association, and the American Statistical Association.^[4]

1. ↑ Borenstein, Michael (1999-06-01). "Jacob Cohen, PhD, 1923-1998". Archives of General Psychiatry. 56 (6): 581. doi:10.1001/archpsyc.56.6.581. ISSN 0003-990X. PMID 23538686.
2. ↑ ^{2.0 2.1} Shrout, Patrick E. (February 2001). "Jacob Cohen (1923–1998)". American Psychologist. 56 (2): 166. doi:10.1037/0003-066X.56.2.166. ISSN 1935-990X.
3. ↑ ^{3.0 3.1} "Jacob Cohen, PhD, 1923-1998". Archives of General Psychiatry. 56 (6). Borenstein, Michael. 1999-06-01. doi:10.1001/archp (inactive 26 July 2026).{{cite journal}}: CS1 maint: DOI inactive as of July 2026 (link) CS1 maint: others (link)
4. ↑ ^{4.0 4.1} Saxon, Wolfgang (1998-02-07). "Jacob Cohen, 74, Psychologist And Pioneer in Statistical Studies". The New York Times. ISSN 0362-4331. Retrieved 2026-06-09.
5. ↑ Cohen, Jacob (2013-05-13). "Statistical Power Analysis for the Behavioral Sciences". Taylor & Francis. doi:10.4324/9780203771587. ISBN 978-1-134-74270-7.