pete22

Karma: 103

pete22 11 Dec 2009 19:07 UTC
1 point
on: You Be the Jury: Survey on a Current Event
I have a different objection to the premise: the presumption of innocence in modern legal systems means that the job of the jury (and by extension the legal teams) is not just to arrive at a probability of guilt but at a certain level of confidence around that probability.

I realize that these can technically be made equivalent by endless “priors”—i.e. a juror walks into the courtroom with a certain set of beliefs, ie probability .8 that someone on trial is guilty, .01 that a sex crime would have been committed by a female rather than a male, etc etc etc, and mentally revises them according to every input—but in any normal intuitive sense the job of a juror is not to answer the exact questions you’ve presented, but to judge the strength of the prosecution’s case from a skeptical viewpoint.

So when you conflate the process/outcome of the trial with an independent, rational probability estimate, I think you make it hard for anyone to give you an impartial answer. And this starts right in the title with “you be the juror”—but it extends all the way to minor points like the use of the term “guilty” which has both legal and colloquial meanings.
What links here?
- komponisto's comment on The Cameron Todd Willingham test by Kevin (6 May 2010 18:17 UTC; 7 points)

pete22 11 Dec 2009 20:49 UTC
3 points
in reply to: mattnewport’s comment on: You Be the Jury: Survey on a Current Event
I just went to Wikipedia and found a more articulate version of what I’m trying to say:

Gardner-Medwin argues that the criterion on which a verdict in a criminal trial should be based is not the probability of guilt, but rather the probability of the evidence, given that the defendant is innocent (akin to a frequentist p-value). He argues that if the posterior probability of guilt is to be computed by Bayes’ theorem, the prior probability of guilt must be known. This will depend on the incidence of the crime, which is an unusual piece of evidence to consider in a criminal trial. Consider the following three propositions:

A: The known facts and testimony could have arisen if the defendant is guilty,

B: The known facts and testimony could have arisen if the defendant is innocent,

C: The defendant is guilty.

Gardner-Medwin argues that the jury should believe both A and not-B in order to convict. A and not-B implies the truth of C, but the reverse is not true. It is possible that B and C are both true, but in this case he argues that a jury should acquit, even though they know that they will be letting some guilty people go free. See also Lindley’s paradox.

I am not really a stats person and I’m not prepared to defend Garder-Medwin’s model as being correct—but right or wrong, it’s a better description than Bayesian inference of most people’s intuitive concept of the task of a juror.

In other words, when I imagine myself as a juror I’m automatically more concerned about a false positive (convicting an innocent person), and I will intuitively try to answer the question “has the prosecution proved its case” rather than “is this person guilty.”

If asked to answer the second question and quantify my odds of guilt, I’m likely to understate them, precisely because I can’t separate that estimate from the real-world effect of a guilty verdict.

Or in your terms, the “question of what probability corresponds to ‘beyond reasonable doubt’ [or whatever the equivalent standard in Italy]” can’t be completely excluded from the question when we imagine ourselves as jurors, only made implicit.

This reminds me slightly of Eliezer’s “true Prisoner’s Dilemma” article, which I really liked. Just as you can’t posit that someone is my confederate (in his case) and then ask me to consider them in a purely selfish, impartial way—you can’t tell me I’m a juror and then ask me to make a purely impartial assessment. I’m describing a much weaker effect than he was, and maybe it’s more socially conditioned than inherent to human nature, but I think the general concept is the same.

So …better to say “forget the fact that there’s even a trial going on, just imagine that tomorrow the absolute truth will be revealed and you have to bet on it now.”

pete22 14 Dec 2009 20:52 UTC
3 points
on: The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom
By far the most important evidence in a murder investigation will therefore be the evidence that is the closest to the crime itself—evidence on and around the victim, as well as details stored in the brains of people who were present during the act.

the evidence against Guédé is such that the hypothesis of her guilt is superfluous—not needed—in explaining the death of Meredith Kercher

I think you’re begging the question here. Those who are convinced that K&S are guilty seem to believe that the evidence from the crime scene itself suggests that Guede could not have been the only participant – i.e. his involvement does NOT completely explain the death of Meredith Kercher. They seem to believe this for two reasons:
1. The various evidence at the crime scene itself of a clean up and/or staged break-in, things like the bra being cut off or the body being moved – hard to attribute to Guede because a. he wouldn’t have had time (is this true?), and b. little effort was taken to remove evidence against Guede himself, even very obvious things like flushing the toilet.
2. I haven’t seen any commenters mention it here, but one of the anti-Amanda sites, in quoting the Micheli report, seemed to imply that Kercher’s injuries were inconsistent with a single attacker.
Your post appears to take for granted that these are not credible arguments, but they seem like a very significant part of the prosecution’s case – and the part that I found hardest to assess without English versions of the Micheli report and other source documents. Can you explain how you reached this level of confidence?

FWIW, I’m not an Amanda-hater …my prior probability of her guilt was 30%, and I’m ready to revise it down. I’m just not sure I fully understand your argument on this point.
What links here?
- Amanda Knox: post mortem by gwern (20 Oct 2011 16:10 UTC; 48 points)

pete22 15 Dec 2009 4:47 UTC
2 points
in reply to: komponisto’s comment on: The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom
You’re right, this is the part I have trouble understanding. Partly because I have trouble separating the facts of this particular case from the theoretical point you’re making. So if you’ll humor me for a second: let’s say you’re the chief of police somewhere, and one of your detectives comes back from a murder scene and tells you “we’ve arrested a prime suspect and we’ve got very strong evidence against him, including an ironclad DNA match that ties him to the murder. but we don’t think he acted alone, because of X, so we want to keep looking for another suspect.”

It sounds like for almost any X, your response would be “Don’t waste your time. Case closed. Your hypothesis that there was another killer is unnecessary to explain the victim’s death.” Is that correct? What kind of X would suffice for you to let your detectives keep investigating?

pete22 15 Dec 2009 5:10 UTC
0 points
in reply to: komponisto’s comment on: The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom
That’s setting the bar pretty high. What about witnesses who claim to have seen two men running from the scene, or heard multiple voices at the time of the murder?

pete22 15 Dec 2009 5:11 UTC
0 points
in reply to: komponisto’s comment on: The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom
Come to think of it, why would a further (unknown) DNA sample even be enough? You’ve got an explanation for the crime. Surely there are far more likely priors than a double murder that would explain a second DNA sample, right? “Similarly incriminating” might not really be possible; much of what made the first sample so incriminating is that it matched a guy who you already had reason to suspect. Or did you mean that an unknown DNA sample would not suffice, only one that matched another suspect?

pete22 15 Dec 2009 17:57 UTC
1 point
in reply to: heyitsnick’s comment on: The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom
I’m with Nick—there are very few primary sources available in English, and none of the stuff people are linking to, even the articles in mainstream media, seems like a completely reliable source to me—especially on all these he said/she said issues of what evidence was actually adduced in court and if so whether it was effectively refuted.

pete22 15 Dec 2009 18:01 UTC
0 points
in reply to: AnnaGilmour’s comment on: The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom
Anna, I’d be curious to see the link on this when you get a chance.

pete22 15 Dec 2009 19:36 UTC
1 point
in reply to: AnnaGilmour’s comment on: The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom
I tried a Google search—I get a few mentions of Mignini firing his coroner, but they either don’t mention a reason or they say it was punishment for leaks to the press. None seem to be from impartial sources, i.e. one is from that truejustice site, another is an article in the Stranger (seattle weekly) by a friend of Amanda’s …the closest thing to a real news site was a Vanity Fair article, and like the others it doesn’t mention the first coroner saying there was one assailant.

This is the problem I mentioned in another comment—all of our info is second- or third-hand. I’m surprised at how comfortable people are citing this stuff. If this was a comparably public case in the US, there’s a good chance the entire reports from both the old and new coroner would be on the Smoking Gun and we could be linking to them directly...

pete22 15 Dec 2009 20:01 UTC
1 point
in reply to: komponisto’s comment on: The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom
OK, fair enough. I think I understand your standard better now. But let’s go back to the actual case. Here’s a quote from that truejustice site’s summary of the Micheli report:

2) Judge Micheli explains that blood evidence proves that Meredith was wearing her bra when she was killed. Nor is it just the blood on her bra which demonstrates this. It’s also where the blood isn’t on her body. He says that Meredith was wearing her bra normally when she laid in the position in which she died, and she was still wearing it for quite some time after she was dead. Her bra strap marks and the position of her shoulder are imprinted in the pool of blood in that position. Meredith’s shoulder also shows the signs that she lay in that position for quite some time.

He asks the question: Who came back, cut off Meredith’s bra and moved her body some time later? It wasn’t Rudy Guede. He went home, cleaned himself up and went out on the town with his friends. Judge Micheli reasons in his report that it could only have been done by someone who knew about Meredith’s death and had an interest in arranging the scene in Meredith’s room. Seemingly who else but Amanda Knox?

She was apparently the only person in Perugia that night who could gain entry to the cottage. And the clasp which was cut with a knife when Meredith’s bra was removed was found on November 2nd when Meredith’s body was moved by the investigators. It was right under the pillow which was placed under Meredith when she was moved by someone from the position in which she died. On that clasp and its inch of fabric is the DNA of Raffaele Sollecito and Amanda Knox. Micheli reasons in his report that Raffaele and Amanda seemed to have returned to the cottage some time after Meredith was dead, cut off her bra, moved her body, and staged the scene in Meredith’s room.

At what point exactly do you part ways with Judge Micheli in that chain of reasoning? To me, his reasoning starts to sound stretched around the middle of the second paragraph. But it sounds like you might have a problem with this logic from the very beginning …? Are you saying the evidence that the body had been moved is just not worth paying attention to?

pete22 16 Dec 2009 0:20 UTC
3 points
in reply to: AnnaGilmour’s comment on: The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom

One thing to remember is that Mignini fired the coroner doing autopsy investigation when that person said it was the injuries of a single perpetrator. He then hired someone who said it was more than one perpetrator. If you would like, I can find a link to back it up. So the original report said one person caused the injuries.

Again, can you give us your source for this? I’m not doubting you, I just want to get an idea of where it comes from.

pete22 16 Dec 2009 3:55 UTC
4 points
in reply to: komponisto’s comment on: The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom
OK, but why do you keep saying “if”? The judge is making an argument on your terms. He is trying not to privilege the hypothesis. He is starting from the premise of Guede’s involvement, and he does find a reason to infer the involvement of someone else. He does not conclude that the trail goes utterly cold, but instead that it leads convincingly to Raffaele and Amanda.

Now, you may disagree with this argument, but I still haven’t heard the substance of your disagreement. All you’ve done is gainsay it.

Don’t get me wrong—I think your original post was a very good explanation of some huge conceptual problems in the way the case against K&S has come together. If I came in believing they were guilty, you would have raised massive doubts in my mind. And that’s no small accomplishment on your part. But it doesn’t follow that no case against them remains. In order to convince me, or anyone else who’s around the average of 35%, that we should lower our odds to your 1-10% range, I think you have to address the facts more directly. It’s not enough to say “there comes a point when you just have to declare...” or that certain DNA evidence “doesn’t count.”

If you were a defense attorney and we were jurors, then you’re right, you’d have your acquittal. But it’s not a juror’s job to distinguish between a 1% and a 35% probability of guilt. To make that case, I don’t think you can just point out weaknesses here and there in the prosecution’s argument—you need to lay out the strongest version of the prosecution’s case, even if you have to put it together for them, and then show step-by-step why it doesn’t lead to a probability higher than 1-10%.

I don’t blame you for not doing that, because as I’ve been saying, the primary sources aren’t available to do it—at least not in objective, quality English translations. I’m just not sure how you can get to such low odds without taking a more granular approach. You’ve suggested that the correct prior is the (very low) odds of someone like Amanda committing homicide, and others have suggested that the correct prior is the (very high) odds of a convicted defendant in a modern legal system being guilty—but these are two ends of a spectrum, not binary alternatives. Finding the correct point on that spectrum is equivalent to assessing the strength of the prosecution’s case.
What links here?
- komponisto's comment on The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom by komponisto (29 Dec 2009 7:11 UTC; 2 points)

pete22 21 Dec 2009 19:30 UTC
1 point
on: Mandating Information Disclosure vs. Banning Deceptive Contract Terms
I think there’s also a sort of commons problem with disclosure relating to time/attention: for any given 5000-word EULA or warranty or credit card disclosure supplement, it’s plausible that someone could have read and understood it. But it’s impossible for anyone to function in the modern world and thoroughly review all the information that’s “disclosed” to them.

In a perfect theoretical world, this wouldn’t be necessary: you would just need a few people to read each standard piece of paperwork and raise hell about particularly unfair or non-market terms, and the rest of us could rely on those signals. For some products, this seems to work well and disclosure is effective at leading to fully-informed transactions. But for many products it doesn’t, and credit cards are a great example. Is there a way to better distinguish the products/services where disclosure is effective from the ones where it isn’t?

pete22 8 Jan 2010 16:14 UTC
2 points
in reply to: Wei Dai’s comment on: Case study: Melatonin
Same here, and I agree it’s puzzling. Especially not wanting to go to bed. With most of my behaviors that don’t have an obvious motivation, I can think it through and figure out what’s going on, but not with this one.

I wonder if it’s a latent anti-bedtime reaction from childhood?

pete22 8 Jan 2010 16:33 UTC
7 points
in reply to: NancyLebovitz’s comment on: Case study: Melatonin
Let’s say it’s midnight, I’m tired, and I’m home alone with nothing better to do. I know I have to get up early and I’ll feel better / be more productive the next day in direct proportion to how much sleep I get. I still just don’t want to go to bed. It requires real force of will not to stay up and find something else to do, even if it just amounts to reading random stuff online or otherwise killing time.

I’ve gotten better at just making myself go to bed anyway in that situation, but I don’t know why it should take any effort in the first place. Going to sleep should – at least occasionally—be my most attractive alternative, even from a short-term perspective. But for some reason it never feels that way.

I don’t have insomnia, nightmares, apnea or any other condition (that I know of) that would make sleep/bed unpleasant – so at least in my case the act of sleep itself doesn’t seem to be a factor.

pete22 10 Feb 2010 20:32 UTC
3 points
in reply to: PlatypusNinja’s comment on: The Craigslist Revolution: a real-world application of torture vs. dust specks OR How I learned to stop worrying and create one billion dollars out of nothing
This was my first thought too. Taking the question further—even if, by some reliable polling method, you could draw a Venn diagram of CL and facebook users, wouldn’t there be a lot of selection bias? If, say, 40% of CL users are also on facebook, by definition they’re probably a lot more tolerant of ads than the other 60%.

pete22 10 Feb 2010 20:50 UTC
4 points
in reply to: PlatypusNinja’s comment on: The Craigslist Revolution: a real-world application of torture vs. dust specks OR How I learned to stop worrying and create one billion dollars out of nothing
Actually, if you click through the link to Buckmaster’s quote, there’s an insta-poll right underneath it: “Should Craigslist take text ads to fund charity?” As of now there are 729 total votes and it’s running 70% against. Facebook may have a little higher overlap with CL’s userbase than ZDnet, but I would think the overlap in both cases is significant. Doesn’t this weigh against the views of any future FB group, especially since (as Platypus points out) a poll should count for more than a petition?

Scott Adams: ‘Mockability Test’

pete224 Feb 2011 0:44 UTC

7 points

17 comments2 min readLW link

pete22 4 Feb 2011 12:49 UTC
5 points
on: Scott Adams: ‘Mockability Test’
Thanks for all the replies. As I said in the post, I also don’t think Adams is completely serious. Here is the weaker version of his argument that I find interesting: if someone can make you (or maybe other rational/informed people) laugh at your beliefs, should that cause you to reassess your level of certainty in those beliefs?

In other words, I don’t think Adams really believes that someone “successfully” mocking your opinions automatically makes them false—but he’s asserting at least some connection between this kind of humor and truth. Which feels right to me, though I can’t really articulate it any better than he did.

Or maybe it’s more of a connection to self-deception—the easier it is to laugh at your own beliefs, the more likely they are to be somehow insincere, regardless of their truth or falsehood.

pete22 4 Feb 2011 12:52 UTC
7 points
in reply to: Costanza’s comment on: Scott Adams: ‘Mockability Test’
None of these examples involves an actual proposition that can be ‘reasonable’ or true or false. I don’t think this is the kind of mockery that Adams is talking about.

pete22

Scott Adams: ‘Mock­a­bil­ity Test’

Scott Adams: ‘Mockability Test’