Jacob Cohen (statistician)

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Jacob Cohen
Born(1923-04-20)April 20, 1923
DiedJanuary 20, 1998(1998-01-20) (aged 74)
Alma materNew York University
Known forCohen's kappa, Cohen's d, and Cohen's h
Scientific career
ThesisA comparative analysis of the factors underlying intelligence test performance of different neuropsychiatric groups (1950)

Jacob Cohen (April 20, 1923 – January 20, 1998) was an American psychologist and statistician best known for his work on statistical power and effect size, which helped to lay foundations for current statistical meta-analysis[1][2] and the methods of estimation statistics. He gave his name to such measures as Cohen's kappa, Cohen's d, and Cohen's h.

Power analysis and significance testing[edit]

In addition to being an advocate of power analysis and effect size, Cohen was a critic of reliance on, and lack of understanding of, significance testing procedures used in statistics, especially misunderstandings of null hypothesis significance testing. In particular, he identified the "near universal misinterpretation of p as the probability that H0 is false, the misinterpretation that its complement is the probability of successful replication, and the mistaken assumption that if one rejects H0 one thereby affirms the theory that led to the test".[3] He encouraged instead a recognition of single studies as exploratory and a reliance on replication for support.


A graduate of City College, he received his PhD in clinical psychology at New York University in 1950. Between 1959 and retirement in 1993 he worked in the psychology department at New York University, latterly as the head of the quantitative psychology group.[4]

He was awarded the Distinguished Lifetime Achievement Award by the American Psychological Association in 1997 and was a fellow of the American Association for the Advancement of Science, the American Psychological Association and the American Statistical Association.[5]

Selected works[edit]

Below are listed some of Cohen's works. Where multiple authors are present, full names are used to facilitate reader searches for other works by those authors.


  1. ^ Cohen's entry in Encyclopedia of Statistics in Behavioral Science
  2. ^ Borenstein, Michael (1999), "Jacob Cohen, PhD, 1923-1998", Archives of General Psychiatry, 56 (6): 581, doi:10.1001/archpsyc.56.6.581, PMID 23538686, archived from the original on August 8, 2007
  3. ^ Cohen, J. (1994). The earth is round (p < .05). American Psychologist, 49(12), 997-1003. doi:10.1037/0003-066x.49.12.997
  4. ^ Wolfgang Saxon (February 7, 1998), "Jacob Cohen, 74, Psychologist And Pioneer in Statistical Studies", New York Times, retrieved May 5, 2010
  5. ^ Saxon, Wolfgang (7 February 1998). "Jacob Cohen, 74, Psychologist and Pioneer in Statistical Studies". The New York Times.

External links[edit]