# assumes prior probability equals 50

## Spanish translation: con una probabilidad inicial del 50 %

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 11:55 Dec 16, 2010
English to Spanish translations [PRO]
Science - Mathematics & Statistics
 English term or phrase: assumes prior probability equals 50 Hi again! The last question! I´m now the DNA test. In the part of the results it says: "This probability of paternity is calculated by comparing to an untested, unrelated man of the North American Hispanic population (assumes prior probability equals .50). This DNA Parentage Test excluded greater than 99.99% of the male population from being the biological father of the tested child". My doub is about the phrase which is in parenthesis "(assumes prior probability equals 50)". Thanks in advance!
 Fernanda1984Argentina Local time: 08:21
Selected response from:

M. C. Filgueira
Local time: 12:21
 thank you!!4 KudoZ points were awarded for this answer

5utilizando una probabilidad a-priori del 50% o utilizando un prior de 50%lrj
5con una probabilidad inicial del 50 %M. C. Filgueira
5la probabilidad "a priori" se estima en 0.5gmarva

16 hrs   confidence:
la probabilidad "a priori" se estima en 0.5

Explanation:
También puede decirse:

"la probabilidad previa se estima en 0.5"

En este caso particular, se dice que un hombre cualquiera tiene una probabilidad de 0.5 de ser el padre biológico de una persona, porque hay dos opciones: puede ser el padre, o no serlo.

Reference: http://quickmedinc.com/terms.html
 gmarvaMexicoLocal time: 05:21Works in fieldNative speaker of: Spanish

48 mins   confidence:
con una probabilidad inicial del 50 %

Explanation:
O: "para el que se supone una probabilidad inicial del 50 %" (pero prefiero "con...", más simple).

Es decir, se compara la probabilidad de que el hombre sometido a la prueba de paternidad sea el padre con la de un hombre X (ficticio) que hubiese tenido relaciones sexuales con la madre y no se hubiese sometido al análisis (en ese caso, la probabilidad es del 50 % : puede ser el padre del niño como puede no serlo).

Mirá lo que dicen en este libro:

"The likelihood that he [a man who is not exclude by the tests] is the actual father is then compared statistically to that of a fictional man who is assumed to have had sexual intercourse with the mother and who is assumed not to be excluded by the test."

Saludos cordiales.

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Note added at 1 día3 horas (2010-12-17 15:08:00 GMT)
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En mi opinión, esto no tiene fundamento.

El adjetivo prior significa existing or happening before something else, or before a particular time (http://dictionary.cambridge.org/dictionary/british/prior_1).

En este caso concreto, el "something else" es, precisamente, la prueba de paternidad. La prior probability es la probabilidad teórica de ser el padre del niño en cuestión que se supone tiene cualquier hombre X que haya tenido relaciones sexuales con la madre (unos nueve meses antes del nacimiento, claro), antes de realizar la prueba de paternidad; creo que se entiende fácilmente que esta probabilidad es de 0,5.

Al comparar los perfiles de ADN del niño y del hombre en cuestión se calcula la probabilidad real de que dicho hombre sea el padre de dicho niño. Si dicha probabilidad es cercana a 0,5 (es decir, similar a la probabilidad teórica inicial), se concluye que dicho hombre no es el padre. Si, en cambio, dicha probabilidad es cercana a 1, se concluye que dicho hombre es muy probablemente (con las técnicas modernas casi puede decirse "seguramente") el padre del niño.

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Note added at 1 día16 horas (2010-12-18 04:10:56 GMT)
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Acabo de darme cuenta de que en la explicación que te di me expresé mejor que en la frase de respuesta: "con una probabilidad inicial/teórica de 0,5", en vez de "50 %". En efecto, aunque en lenguaje coloquial las probabilidades se expresan con frecuencia como porcentajes, desde el punto de vista matemático se trata de un número comprendido entre 0 y 1.

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 M. C. FilgueiraLocal time: 12:21Works in fieldNative speaker of: SpanishPRO pts in category: 66
 thank you!!

26 days   confidence:
utilizando una probabilidad a-priori del 50% o utilizando un prior de 50%

Explanation:
Most paternity tests use Bayesian statistics. In Bayesian statistics, the probability of an event is calculated based on two factors: [i] the outcome of an experiment (in our case the DNA test) and [ii] a prior probability, also called just “prior” (they say “prior” because this probability is assigned _before_ performing the experiment). The probability of an event, which Bayesians call “posterior probability”, is thus proportional to its prior and to the outcome of the experiment.

Ideally, priors are assigned according to previous knowledge. In many cases, like paternity tests, it is very difficult (if not impossible) to objectively assign prior probabilities. Bayesian statisticians solve this problem by using “uninformative prior distributions”, which in colloquial language means that every possible outcome of an experiment is assigned a constant prior. In paternity tests, the experiment outcomes are two: “is the father/mother” and “isn’t the father/mother”. Thus, as the sum of the probabilities of all the possible experiment outcomes must equals 1 and as we want to use a non informative prior, a prior of 0.5 is used.

In short, best translations would be “utilizando una probabilidad a-priori del 50%” or “utilizando un prior de 50%”.

 lrjSpecializes in fieldNative speaker of: Spanish

 Dec 16, 2010 - Changes made by Laureana Pavon: Field (write-in) Law » (none) Dec 16, 2010 - Changes made by Laureana Pavon: Field Law/Patents » Science Field (specific) Law (general) » Mathematics & Statistics

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