Re: Pienso, luego Dudo – Capítulo 18b


Leandro Yampolsky dijo:

Aca encontre la explicacion del ejemplo que dio Bunge en la charla (que era dificil de entender porque cada 30 segundos alejaba el microfono a 1 metro de su boca) (Chasing Reality, 4. Causation and Chance: Apparent or Real?, 9. Bayesianism Is Hazardous):

To appreciate the enormity of the Bayesian attempted counter-revolution,

consider, for instance, the relation between the HIV virus and AIDS. It is well

known that, whereas those who have this disease test HIV-positive, the converse

is not true: some individuals have lived with the virus for a decade or

more without developing AIDS. Suppose then that a given individual has

contracted that virus, and that we wish to ascertain the probability that he

also has, or will soon develop, AIDS. Presumably, a Bayesian would set

Pr(AIDS | HIV) = Pr(HIV | AIDS) Pr(AIDS) / Pr(HIV). Further, since the individual

in question has tested HIV-positive, our Bayesian is likely to set Pr(HIV)

= 1. And, since it is known that whoever has AIDS also has the HIV virus,

Pr(HIV | AIDS) = 1. Thus, Bayes’s formula simplifies to Pr(AIDS | HIV) =

Pr(AIDS). However, this is known to be false: in fact, HIV is necessary but not

sufficient to develop AIDS. So, if AIDS researchers were to adopt Bayesianism,

they would not try to discover the causes that, jointly with HIV infection, lead

to AIDS.

Se entendió más o menos. Lástima que Bunge eligió el ejemplo del HIV que es bastante malo para esto.