Comments on: Open Thread

By: William Worlton

William Worlton — Thu, 01 May 2008 16:24:25 +0000

Exponential growth is typically limited in some way, so that it becomes “S”-shaped, i.e., it approaches an asymptote. Such trends follow the differential equation: dN/dt = k•N•(1-L/N), so as N approaches the limit, L, the factor (1-L/N) approaches zero, thereby stopping the exponential component’s influence in the simpler equation dN/dt = k•N, whose solution was exponential. The “S”-shaped curve is pervasive in technological change, and to use simple exponentials is to argue that there are no limits to growth.

A good rule of thumb is: All trends have limits.

By: Hopefully Anonymous

Hopefully Anonymous — Sun, 27 Apr 2008 04:27:39 +0000

What does this mean? Anything rational? Risk vs. Gamble? Gamble here means taking a very large risk past a certain threshhold? Since this guy is a grad student in journalism, I think he should be held to a high standard in terms of lanugage use.

http://www.nytimes.com/2008/04/27/opinion/27murphy.html?ref=opinion

“In his closing arguments last week, the prosecutor, Charles Testagrossa, said, “We ask the police to risk their lives to protect ours.” I agree. But they shouldn’t have to gamble with them.

Kyle K. Murphy, a former lieutenant in the New York Police Department, is a graduate student in journalism at Columbia.”

By: Hopefully Anonymous

Hopefully Anonymous — Thu, 24 Apr 2008 00:52:21 +0000

Any overcomingbias headliners doping for cognitive advantage? There’ve been some articles on that recently in the media. Thoughts on those articles?

By: Z. M. Davis

Z. M. Davis — Wed, 23 Apr 2008 22:30:01 +0000

I should add--anonymous, I would mention to your acquaintance that one of the many empirically demonstrated ways in which real people depart from Bayesianity is that "naive subjects do not distinguish between p(A|B) and p(B|A) in most circumstances" (Rational Choice in an Uncertain World). These can be very different quantities. So it might be the case that P(A|B) is high and P(B|A) is low, and a false stereotype forms that "As are generally Bs."

By: Z. M. Davis

Z. M. Davis — Wed, 23 Apr 2008 17:31:49 +0000

Anonymous, it makes me sad for ideological reasons too, but your acquaintance is correct: it is rational to use information about average group differences to make probabilistic inferences about an individual.

Of course, as you acquire information about an individual, the relevance of group information in the form of stereotypes quickly vanishes–and of course we need to worry about inaccurate stereotypes, and the possibility of stereotypes influencing behavior to the point of becoming “self-fulfilling prophecies”–but the basic point, that it’s not wrong to generalize if you do it right, holds.

By: Richard

Richard — Wed, 23 Apr 2008 17:05:15 +0000

Anonymous - was your friend attempting to morally justify, or just epistemically justify stereotyping? I don't think Bayes has much to say about the former issue. See my old post on Racial Profiling (and especially Blar's comment) for further discussion.

By: anonyous

anonyous — Wed, 23 Apr 2008 16:29:34 +0000

Hmm … I seem to have posted this on an older open thread by accident. I’ll repost it here.

I’m wondering if Bayes’ theorem can be used to justify racial stereotyping. I’m hoping it can’t, for ideological reasons obviously, but someone I know recently made what seemed to be a reasonably strong case for it, which I’m finding difficult to refute because I don’t have a solid grounding in probability, but he does (or at least claims that he does).

If this is a misconception, please dispel it for me so that I can refer my friend to your explanation (that’s right: I’m asking the Bayesian gods to do it for me. Sorry, I’m just very busy right now, and I figure you’re up to the job, and this is a place where more people will see it).

By: Caledonian

Caledonian — Wed, 23 Apr 2008 14:52:15 +0000

Hopefully, I’m surprised you see my blog posts as obviously libertarian, especially on medicine. I have almost never taken positions here regarding more versus less government intervention.

I think even asking the question is considered to be ‘libertarian’; good liberals/conservatives don’t ask whether the policies they favor are effective, they’re supposed to know they are. Asking implies doubt and skepticism, which are sins.

By: Hopefully Anonymous

Hopefully Anonymous — Wed, 23 Apr 2008 06:34:32 +0000

Apparently there is a completion bias, in which we’re more motivated to complete something close to finished, then to spend our energy in other areas that would benefit ourselves more. I’m concerned that completion bias may play a role in how scientists and thinkers are rewarded (are they rewarded more for finishing something, then sharing unfinished work? I don’t know of prestigious publication venues for partially finished work.)

Thus, Aleks Jekulon (sp?) in my opinion deserves praise for putting a lot of unfinished work of his on the internet for the rest of us to look at. Thoughts from the regular OvercomingBias contributors about completion bias and how scientists and thinkers are rewarded?

Aleks Jekulon’s website as a model:

http://www.stat.columbia.edu/~gelman/blog/

By: Hopefully Anonymous

Hopefully Anonymous — Sat, 12 Apr 2008 04:09:26 +0000

Robin, nope. I interpret you as doing a little dance where you seem honest about the data, but always seem careful to put some effort of framing the discussion of the data such that your posture is “here are ways that with less government regulation/funding we can maintain or improve on the health status quo”. Even though the data that you seemly to fairly present often seems equally framable as “here are some ways in which government regulation/funding DOES get better results than the lack of it”.

It seems, in my opinion to be dialectic-seeking, rather than enlightenment-seeking posturing. Sort of like, audiences seem more attracted to media that has a classic oppositional/dualistic undercurrent, such as individualist vs. collectivist, and often award more status and attention to participants in these dialectics, over people who put out media that seems more limited to empirical inquiry and problem-solving. I suspect this is a deeply rooted primate aesthetics. Perhaps an intuition that it’s more important of observing two alphas battle it out, and of choosing the right one’s side to be on, than it is to observe one’s natural environment and make decisions of how to survive in it without considering one’s relations with dominant and challenger alphas.

If I get a chance I’ll try to rewrite some of your recent and classic posts on this topic, as I imagine they could be without what I think is the nonexplicit libertarian/individualist/small govt. etc. posturing.

ps I ended up adding here and there to this post, without a lot of time to edit it overall, so my apologies for any disorganization or incoherence.