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The quiz Daniel Kahneman wants you to fail

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Re: The quiz Daniel Kahneman wants you to fail

#101

Post by jules »

bfung wrote: post #69
Uhhrrr wrote: post #6

The engineer/lawyer problem explanation (spoilers) is only correct in a world where lawyers and engineers have all the same characteristics. That the sampled individual is a man will skew things all by itself. Of the lawyers, approximately 40% will be women, whereas only 11% of the engineers. So our samplee could be one of 27 engineers or 42 lawyers - we've already bumped Peng from .3 to .39! That he likes math puzzl…

30 engineers, 70 lawyers, the probability of being an engineer is 30%. What Jack likes to do is irrelevant. Why can't a lawyer like math and dislike politics (winning a case framed by certain rules is just a puzzle/game to hack)?

Here's an alternative story:

To the question "Are you an engineer?", Jack answered "Yes".

Would you still argue that the probability is 30% that he is an engineer? A lawyer can claim to be an engineer, after all. However I think it is clear that if we actually did the experiment, it would be much more likely than 30% that Jack is an engineer. A way of testing what you really believe the probability to be is this: I bet you a dollar that Jack is an engineer. If you wouldn't, that means that you really believe the probability to be larger than 50%.

This is because the probability that he answers yes to the question is much higher when he is in fact an engineer than when he is a lawyer. Bayes' law says:

    P(E|Y) = P(E) * P(Y|E)/P(Y)
You should read P(A|B) as "the probability that A is true given that B is true". In this case E = "a person is an engineer" and Y = "a person answers yes to the question 'are you an engineer?'". As you can see the original P(E) = 30% gets multiplied by P(Y|E)/P(Y) given the information that the person answered yes. The probability that a person answers yes given that he is an engineer is higher than the general probability that a person answers yes. So P(Y|E)/P(Y) > 1. So P(E|Y) > 30%.

This same law applies to other characteristics, for example Y = "person likes mathematics".

Re: The quiz Daniel Kahneman wants you to fail

#102

Post by Retric »

elnerdo wrote: post #28
diego wrote: post #14

Earlier quoted context omitted.

Exactly. Here's the example used in Kahneman's book: "Dick is a 30-year-old man. He is married with no children. A man of high ability and high motivation, he promises to be quite successful in his field. He is well liked by his colleagues. This description was intended to convey no information relevant to the question of whether Dick is an engineer or a lawyer." The description in the quiz is very different.

This still conveys a lot of information. Engineering is more male-heavy than lawyering.

Your assuming a US bias, the sample could have come from India which has different ratios.

Re: The quiz Daniel Kahneman wants you to fail

#103

Post by icefox »

kia wrote: post #61

Question three about dates is pretty much Anchoring Effect: http://en.wikipedia.org/wiki/Anchoring Also an interesting reference about anchoring and electric cars from the above Wikipedia article: http://www.treehugger.com/cars/nissans-leaf-creates-a-new-an...

The thing is question three is about dates and question three B is about how happy you are so the two are suppose to be related. If it was question three and question four maybe, but not when they put the two questions together.

Re: The quiz Daniel Kahneman wants you to fail

#104

Post by condiment »

prof_hobart wrote: post #86
bfung wrote: post #69

Earlier quoted context omitted.

30 engineers, 70 lawyers, the probability of being an engineer is 30%. What Jack likes to do is irrelevant. Why can't a lawyer like math and dislike politics (winning a case framed by certain rules is just a puzzle/game to hack)?

It's not that a lawyer can't like maths or dislike politics. The issue is whether they are less likely to on average. From my personal experience of knowing several of both groups, I would say that on average the lawyers I know are less interested in maths than the engineers and more interested in politics than them. It doesn't apply universally (some of the engineers I know are obsessed by politics, just not all of…

I think the point that many are missing is that is not known for certain that an engineer is more likely to enjoy certain hobbies over others. People use their personal experience to develop a heuristic which this test is designed to reveal.

Getting hung up over the specificity of the hobbies and interests and the likelihood of those hobbies and interests representing either or a lawyer or an engineer is irrelevant, because the only factual data that was provided by the questioner is that 30% of the participants were engineers, and 70% were lawyers.

Re: The quiz Daniel Kahneman wants you to fail

#105

Post by wizzard »

screwt wrote: post #73
jfoutz wrote: post #50

Earlier quoted context omitted.

a frequentist would take issue with the two sons, one born on a tuesday problem. you can actually count up the permutations. let's say we have 10 engineers, 9 of them are male. we also have 10 lawyers, 6 of them are male. Let's say one in 10 people likes doing math on the weekend. There are 90 out of 100 ways to have a group of male engineers, one of which who likes math, but only 60 out of 100 ways to do the same wi…

> This isn't bayesian, this is just counting boxes on a permutation table. It's the same thing. Bayes' theorem allows you to shortcut straight to the answer without having to draw out a full probability tree / permutation table. But the underlying math is the same - in each case you have a different probability of B given A, versus B given (not A).

Personally I wouldn't call it "Bayesian" so much as just "a conditional probability." The question doesn't ask what the probability is that a randomly selected participant is an engineer, it asks what the probability is that a participant is an engineer given that he has "typical" engineer-like traits.

But then yes, ideally you could use Bayes' Rule to find that probability.

Re: The quiz Daniel Kahneman wants you to fail

#106

Post by andylei »

ssp wrote: post #77
chimeracoder wrote: post #53

Earlier quoted context omitted.

> I never understand why economists think that a rational actor would consider them equivalent They don't: https://en.wikipedia.org/wiki/Expected_utility In short, there are three types of people: risk-averse, risk-neutral, and risk-preferring. (In the general case, people can exhibit all three types of behavior at different income levels, but let's keep things simple). Imagine a graph, with income on the x-axis and…

Distinguishing between risk-averse/neutral/preferring seems like begging the question to me. Couldn't there be an objective answer to which of three behaviors is the most rational in some situation?

the term "rational" for economists has a very specific meaning. an actor behaving "rationally" has a utility function that satisfies some set of properties, and when confronted with choices, chooses in a way that maximizes that utility function.

these are the properties of a "rational" utility function: http://en.wikipedia.org/wiki/Rational_choice_theory#Actions....

Re: The quiz Daniel Kahneman wants you to fail

#107

Post by SilasX »

colanderman wrote: post #23

The questions involving "90% chance of $1000 or 100% chance of $900" always bother me. I never understand why economists think that a rational actor would consider them equivalent; they're not , unless you are making that choice many many times. But if I'm given that chance once (which is presumably what most participants assume, since that's not a choice that comes up often in one's life), it's really then a choice…

Agree 100%. There is so much wrong with all of these questions, and that's only one of the things wrong with this particular one.

In addition to that, there's very good reason for someone to act differently when it's a gain vs. loss at stake. For one thing, this difference is the whole reason that an insurance industry can exist! (And insurance, in turn, is the only reason many kinds of utility-enhancing ventures can exist at all!)

I used to wonder what the point of insurance was when you could just bear the risk yourself, but then I had an insight (that no one else arguing with me managed to bring up):

Diminishing marginal utility implies increasing marginal disutility!

Utility as a function of how much of a good G that you have, usually increases at a decreasing rate. The first n units provide more of a utility gain than the 2nd n units, and so on. For much the same reason, losing your first n units isn't as bad as losing the 2nd n units, and so on. (It may help to visualize U(n) as a logarithmic curve.)

This is why people can rationally regard it as better to have a guaranteed loss of (at least) N rather than a (1/x) chance of losing x times N, while not also buying a lottery ticket for N that offers a (1/x) chance of gaining x times N. And that, in turn, shows the fundamental asymmetry between insurance and gambling.

Kahnemann must be on the phone with VF right now demanding they correct this article in about ten places.

Re: The quiz Daniel Kahneman wants you to fail

#108

Post by BobNeumann »

redxaxder wrote: post #35
colanderman wrote: post #23

The questions involving "90% chance of $1000 or 100% chance of $900" always bother me. I never understand why economists think that a rational actor would consider them equivalent; they're not , unless you are making that choice many many times. But if I'm given that chance once (which is presumably what most participants assume, since that's not a choice that comes up often in one's life), it's really then a choice…

By rescaling the numbers, the two questions can be turned into: - "Would you pay $900 for a 90% chance to win $1000?" - "Would you pay $100 for a 10% chance to win $1000?" So the distribution of results really is different. It's not just a phrasing trick. I would still say no to the first and yes to the second. I like positive outliers more than negative ones. This doesn't seem irrational to me.

I agree completely with a minor tweak: "Would you RISK $900 for a 90% chance to win $1000?" "Would you RISK $100 for a 10% chance to win $1000?"

It's all about managing the risk: generally speaking, I can afford to risk $100, but not $900. Furthermore, I've already spent/borrowed the second $1000 (We're TAKING my existing money, which I presumably have already planned on having). So the first is a windfall, but the second is a real need. So I WON'T risk a large amount of money for a windfall, but I WILL risk a small amount in order to meet a real need. I'd say that's 100% rational.

Bob

Re: The quiz Daniel Kahneman wants you to fail

#109

Post by nkurz »

jacques_chester wrote: post #17
atuladhar wrote: post #5

I recently read Kahneman's 2011 book "Thinking, Fast and Slow" -- it should probably be required reading for everybody who's in charge of making decisions that affect a lot of people.

I have to second this advice, even though I'm halfway through it. Kahneman has spent decades investigating biases and cognitive error. And it turns out he's not all that bad at popularising his and related research. Of particular fascination (and frustration!) are the little examples he liberally sprinkles throughout the book. Small quizzes, questions and the like for the reader to try. Try as I might, I have consist…

I'm halfway through it as well, but have a less positive impression. I came into it with a lot of respect for Kahneman and his research, but the first half of book is extremely flat. Much like the reaction here to this Vanity Fair teaser, I constantly find myself quibbling with the examples, and disagreeing with the explanations.

I'm not sure who to blame, though. I think the book was written over a considerable period of time. Perhaps Kahneman's standards have changed? Perhaps there were multiple editors involved, some of whom (like the Vanity Fair author) didn't really understand the material? Or perhaps the editor was great, but only worked on some of the chapters.

I'd offer a much less enthusiastic bottom line: It's a frustrating book, but you should read it anyway. Skip to Chapter 20 "The Illusion of Validity" if you get bogged down.

Re: The quiz Daniel Kahneman wants you to fail

#110

Post by BobNeumann »

prof_hobart wrote: post #86
bfung wrote: post #69

Earlier quoted context omitted.

30 engineers, 70 lawyers, the probability of being an engineer is 30%. What Jack likes to do is irrelevant. Why can't a lawyer like math and dislike politics (winning a case framed by certain rules is just a puzzle/game to hack)?

It's not that a lawyer can't like maths or dislike politics. The issue is whether they are less likely to on average. From my personal experience of knowing several of both groups, I would say that on average the lawyers I know are less interested in maths than the engineers and more interested in politics than them. It doesn't apply universally (some of the engineers I know are obsessed by politics, just not all of…

I agree. In many areas of pop-culture we seem to have a lot of people trying to convince us that "We don't know what we know", often with hilarious results. Like the EU officials who ruled that "drinking water has not been shown to reduce dehydration."

The more I see this trend, the more stubbornly I find myself clinging to "What I know"

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