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Bruno de Finetti

 

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Bruno de Finetti



 
 
Bruno de Finetti (June 13, 1906 - July 20, 1985) was an Italian
Italy

Italy , officially the Italian Republic , is a country located on the Italian Peninsula in Southern Europe and on the two largest islands in the Mediterranean Sea, Sicily and Sardinia....
  probabilist and statistician
Statistician

Statisticians work with theoretical and applied statistics in both the private and public sectors. The core of that work is to measure, interpret, and describe the world and human activity patterns within it....
, noted for the "operational subjective" conception of probability
Probability

Probability, or wikt:chance, is a way of expressing knowledge or belief that an Event will occur or has occurred. In mathematics the concept has been given an exact meaning in probability theory, that is used extensively in such areas of study as mathematics, statistics, finance, gambling, science, and philosophy to draw conclusions about t...
. The classic exposition of his distinctive theory is the 1937 "La prévision: ses lois logiques, ses sources subjectives," which discussed probability founded on the coherence of betting odds and the consequences of exchangeability.

inetti proposed a thought experiment
Thought experiment

A thought experiment , sometimes called a Gedanken experiment, is a proposal for an experiment that would test or illuminate a hypothesis or theory....
 along the following lines (described in great detail at coherence (philosophical gambling strategy)
Coherence (philosophical gambling strategy)

In a thought experiment proposed by the Italian probabilist Bruno de Finetti in order to justify Bayesian probability, an array of wagers is coherent precisely if it does not expose the wagerer to certain loss regardless of the outcomes of events on which he is wagering, provided his opponent chooses judiciously....
): You must set the price of a promise to pay $1 if there was life on Mars 1 billion years ago, and $0 if there was not, and tomorrow the answer will be revealed.






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Bruno de Finetti (June 13, 1906 - July 20, 1985) was an Italian
Italy

Italy , officially the Italian Republic , is a country located on the Italian Peninsula in Southern Europe and on the two largest islands in the Mediterranean Sea, Sicily and Sardinia....
  probabilist and statistician
Statistician

Statisticians work with theoretical and applied statistics in both the private and public sectors. The core of that work is to measure, interpret, and describe the world and human activity patterns within it....
, noted for the "operational subjective" conception of probability
Probability

Probability, or wikt:chance, is a way of expressing knowledge or belief that an Event will occur or has occurred. In mathematics the concept has been given an exact meaning in probability theory, that is used extensively in such areas of study as mathematics, statistics, finance, gambling, science, and philosophy to draw conclusions about t...
. The classic exposition of his distinctive theory is the 1937 "La prévision: ses lois logiques, ses sources subjectives," which discussed probability founded on the coherence of betting odds and the consequences of exchangeability.

Work

De Finetti proposed a thought experiment
Thought experiment

A thought experiment , sometimes called a Gedanken experiment, is a proposal for an experiment that would test or illuminate a hypothesis or theory....
 along the following lines (described in great detail at coherence (philosophical gambling strategy)
Coherence (philosophical gambling strategy)

In a thought experiment proposed by the Italian probabilist Bruno de Finetti in order to justify Bayesian probability, an array of wagers is coherent precisely if it does not expose the wagerer to certain loss regardless of the outcomes of events on which he is wagering, provided his opponent chooses judiciously....
): You must set the price of a promise to pay $1 if there was life on Mars 1 billion years ago, and $0 if there was not, and tomorrow the answer will be revealed. You know that your opponent will be able to choose either to buy such a promise from you at the price you have set, or require you to buy such a promise from your opponent, still at the same price. In other words: you set the odds, but your opponent decides which side of the bet will be yours. The price you set is the "operational subjective probability" that you assign to the proposition on which you are betting. This price has to obey the probability axioms if you are not to face certain loss, as you would if you set a price above $1 (or a negative price). By considering bets on more than one event de Finetti could justify additivity. Prices, or equivalently odds
Odds

In probability theory and statistics the odds in favour of an event or a proposition are the quantity , where p is the probability of the event or proposition....
, that do not expose you to certain loss through a Dutch book
Dutch book

In gambling a Dutch book or lock is a set of odds and bets which guarantees a profit, regardless of the outcome of the gamble. It is associated with probability implied by the odds not being Coherence ....
 are called coherent.

De Finetti is also noted for de Finetti's theorem
De Finetti's theorem

In probability theory, de Finetti's theorem explains why exchangeable random variables observations are conditionally independent given some unobservable quantity to which an epistemic probability probability distribution would then be assigned....
 on exchangeable
De Finetti's theorem

In probability theory, de Finetti's theorem explains why exchangeable random variables observations are conditionally independent given some unobservable quantity to which an epistemic probability probability distribution would then be assigned....
 sequences of random variable
Random variable

In mathematics, random variables are used in the study of Randomness and probability. They were developed to assist in the analysis of Game of chance, stochastic events, and the results of experiment by capturing only the mathematical properties necessary to answer probability questions....
s. De Finetti was not the first to study exchangeability but he brought the subject to greater visibility. He started publishing on exchangeability in the late 1920s but the 1937 article is his most famous treatment.

In 1929, de Finetti introduced the concept of infinitely divisible probability distributions.

He also introduced de Finetti diagram
De Finetti diagram

A de Finetti diagram is a ternary plot used in population genetics. It is named after the Italy statistics Bruno de Finetti and is used to graph the genotype frequency of populations, where there are two alleles and the population is diploidy....
s for graphing genotype
Genotype

The genotype is the trait we can't see. The genotype is the Genetics constitution of a cell, an organism, or an individual usually with reference to a specific character under consideration....
 frequencies.

Life

De Finetti was born in Innsbruck
Innsbruck

Innsbruck is the Capital of the federal state of Tyrol in western Austria. It is located in the Inn River Valley at the junction with the Wipptal , which provides access to the Brenner Pass, some 30 km south of Innsbruck....
, Austria
Austria

Austria , officially the Republic of Austria , is a landlocked country in Central Europe. It borders both Germany and the Czech Republic to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the west....
 and studied mathematics at Milan University. After graduation, he did not pursue an academic career but worked as an actuary and a statistician. He published extensively (17 papers in 1930 alone, according to Lindley) and acquired an international reputation in the small world of probability mathematicians. He won a chair in Financial Mathematics at Trieste University (1939). In 1954 he moved to the University of Rome, first to another chair in Financial Mathematics and then, from 1961 to 1976, one in the Calculus of Probabilities. De Finetti developed his ideas on subjective probability in the 1920s independently of Frank P. Ramsey
Frank P. Ramsey

Frank Plumpton Ramsey was a United Kingdom mathematician who, in addition to mathematics, made significant contributions in philosophy and economics....
. He only became known in the Anglo-American statistical world in the 1950s when L. J. Savage, who had independently adopted subjectivism
Bayesian inference

Bayesian inference is statistical inference in which evidence or observations are used to update or to newly infer the probability that a hypothesis may be true....
, drew him into it; another great champion was Dennis Lindley
Dennis Lindley

Dennis Victor Lindley is a British statistics, decision theorist and leading advocate of Bayesian statistics.Dennis Lindley grew up in the south-west London suburb of Surbiton....
. De Finetti died in Rome
Rome

Rome is the capital city of Italy and Lazio, and is Italy's largest and most populous city, with 2,724,347 residents in an urban area of some ....
.

The de Finetti Award, presented annually by the European Association for Decision Making, is named after him.

Bibliography

See Works on


de Finetti in English

(The following are translations of works originally published in Italian or French.)
  • "Probabilism: A Critical Essay on the Theory of Probability and on the Value of Science," (translation of 1931 article) in Erkenntnis, volume 31, September 1989. The entire double issue is devoted to de Finetti's philosophy of probability.
  • 1937, “La Prévision: ses lois logiques, ses sources subjectives,” Annales de l'Institut Henri Poincaré,
- "Foresight: its Logical Laws, Its Subjective Sources," (translation of the in French) in H. E. Kyburg and H. E. Smokler (eds), Studies in Subjective Probability, New York: Wiley, 1964.
  • Theory of Probability, (translation by AFM Smith of 1970 book) 2 volumes, New York: Wiley, 1974-5.


Discussions

  • D. V. Lindley
    Dennis Lindley

    Dennis Victor Lindley is a British statistics, decision theorist and leading advocate of Bayesian statistics.Dennis Lindley grew up in the south-west London suburb of Surbiton....
    , "Bruno de Finetti, 1906-1985 (Obituary)" Journal of the Royal Statistical Society
    Journal of the Royal Statistical Society

    The Journal of the Royal Statistical Society is a series of three peer-reviewed statistics journals published by Blackwell Publishing for the London-based Royal Statistical Society....
    , Series A
    , 149, p. 252 (1986).
The following books have a chapter on de Finetti and references to further literature.
  • Jan von Plato, Creating Modern Probability : Its Mathematics, Physics, and Philosophy in Historical Perspective, Cambridge: Cambridge University Press, 1994
  • Donald Gillies, Philosophical Theories of Probability, London: Routledge, 2000.


External links

  • [https://finetti.meb.uni-bonn.de Generate finetti diagrams online]


There is another photo at
  • on the page.
  • from the Stanford Encyclopedia of Philosophy. De Finetti's views are discussed in Section 3.5 of this article.