DanielLC comments on Hearsay, Double Hearsay, and Bayesian Updates - Less Wrong

47 Post author: Mass_Driver 16 February 2012 10:31PM

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Comment author: DanielLC 15 February 2012 02:29:32AM 1 point [-]

Why can't they just say that each additional layer makes it weaker evidence? For example, hearsay is 50% as strong as seeing it., double hearsay is 25% as strong, triple hearsay is 12.5% as strong, etc.

Comment author: gwern 15 February 2012 10:53:57PM *  10 points [-]

http://hanson.gmu.edu/extraord.pdf

"Extraordinary claims require extraordinary evidence. But on uninteresting topics, surprising claims usually are surprising evidence; we rarely make claims without sufficient evidence. On interesting topics, however, we can have interests in exaggerating or downplaying our evidence, and our actions often deviate from our interests. In a simple model of noisy humans reporting on extraordinary evidence, we find that extraordinary claims from low noise people are extraordinary evidence, but such claims from high noise people are not; their claims are more likely unusual noise than unusual truth. When people are organized into a reporting chain, noise levels grow exponentially with chain length; long chains seem incapable of communicating extraordinary evidence."

Comment author: JoshuaZ 15 February 2012 05:12:26AM 7 points [-]

That's not a great system. The numbers aren't necessarily going to be the same from case to case, and having actual numbers in real life that don't come from very careful evaluations can easily lead to the illusion of precision where it doesn't exist.

Comment author: shminux 15 February 2012 03:21:14AM 11 points [-]

Lawyers don't calculate probabilities, juries don't understand them, so exact numerical values are irrelevant.

Comment author: Viliam_Bur 15 February 2012 10:21:13AM 13 points [-]

Also I would say people don't like probabilistic arguments used in justice. Punishing someone for a high probability that they did something, feels very unfair. But in this universe, this is all we can have.

Would it feel fair to imprison someone because there is a 50% probability they did something wrong? How about 80%? 90%? 99%? People like to pretend that there are some magical values called "reasonable doubt" and "beyond a shadow of doubt" where probabilities stop being probabilities and become a separate magisterium.

We are not good at dealing with probabilities and what we intuitively seek is probably a social consensus -- if everyone important thinks the guy is guilty, then it is safe to punish him. We are trying to be more fair than this, and partially we are succeeding, and partially we are trying to do the impossible, because we can never get beyond probabilities. But there are huge inferential gaps that prevent explaining this in the court.

Comment author: Will_Newsome 15 February 2012 10:16:40PM 0 points [-]

There is a very important sense in which a 99% chance and certainty are in separate magisteria.

Comment author: Bruno_Coelho 25 February 2012 07:44:23AM -1 points [-]

Add, they don't are specialists like mathematicians or cognitive scientists(hard), and the ability to judge the culpability of someone is pretty limited, like non-lawyers.

Comment author: TobyBartels 03 March 2012 08:17:01AM 1 point [-]

This comment is very difficult to read. Suggestion: write it in proper Portuguese, and I will translate it into English. (I am guessing Portuguese from your name. Any other common language should work.)

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