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33 Questions

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Re: 33 Questions

#111

Post by _sh »

ketralnis wrote: post #106
stbullard wrote: post #41

Fun to think about, but in the real world, no question neatly divides people, even the gender one. To quote Reddit's u/tailcalled[1], the exo-software/meatspace world is even less standardized than the software world: Falsehoods programmers believe about gender: http://www.cscyphers.com/blog/2012/06/28/falsehoods-programm... Falsehoods programmers believe about names: http://www.kalzumeus.com/2010/06/17/falsehoods-pr…

> even the gender one Sure, but if you ask "do you consider yourself classically male" and "do you consider yourself classically female", you'll get the vast majority of people, so you can still eliminate large swaths of population with either of these.

The interesting nature of the problem is that you can't just 'eliminate swathes', your question must evenly divide the entire population.

Re: 33 Questions

#112

Post by yiransheng »

If anyone is interested in seeing such a application in a fictional setting, I suggest the anime Death Note, if nothing else for its entertainment value. For those who are familiar with the story, the questions L asked in order to narrow down Kira suspects to a limited demographics in a small region in Japan, among billions of candidates, were some good ones. A good article that analyzes the plot from a information theory perspective: [http://www.gwern.net/Death%20Note%20Anonymity](http://www.gw....

Re: 33 Questions

#114

Post by Erwin »

powrtoch wrote: post #33

I don't think this problem is solvable in any elegant form, but it is solvable. You'll just end up with massively conjunctive questions that you can't even hold in your head at once, like "27: Are you a non-practicing Catholic with exactly three children, or an asian owner of a minivan produced between 1998 and 2004 that isn't green, or a licensed boat mechanic with astigmatism, or..." and so on for the next 6 pages.…

Sounds like a premise for a dystopian sci-fi story: a future where every identity is exactly planned, where everyone's life is determine by ... 33 bits. Donald Sutherland can be the benevolent ruler that tells the protagonist how the unbridled greed of the 21st century brought us here (Hollywood adaptation can add an ironic anti-consumerist twist).

Perhaps this could be a retro sci-fi a la "Brazil", with each person carrying around a punch card with his 33-bits on them. A computer error means two people are issued the same bit pattern. In a defining shot, they hold up their punch cards up against the sun and see the holes line up. Maybe an Egyptian tomb opens too!

Re: 33 Questions

#116

Post by vacri »

How many questions would you need to differentiate between identical twins, particularly if they live and work together? Take identical twin sons of a subsistence farmer - they live together, work together on the same things, know the same people, have the same genetic makeup, and whichever was the first twin born may not have been recorded. You could ask their names, but that's not a yes/no question.

Or even twins who are still babies, no work required? Some cultures wouldn't even have named them yet.

Re: 33 Questions

#118

Post by incompatible »

vacri wrote: post #116

How many questions would you need to differentiate between identical twins, particularly if they live and work together? Take identical twin sons of a subsistence farmer - they live together, work together on the same things, know the same people, have the same genetic makeup, and whichever was the first twin born may not have been recorded. You could ask their names, but that's not a yes/no question. Or even twins w…

Multiple births would be bad enough, and then you have people with dementia who can't remember the answer to most of the questions, and people in a coma who can't answer questions at all. The chance of succeeding with this exercise is approximately zero.

Re: 33 Questions

#119

Post by jules »

upquark wrote: post #95
abentspoon wrote: post #69

It's not enough to find 33 independent questions that evenly split the world's population. An optimal, though inelegant solution to that goal might look something like this: "Is the {1..33}th bit of sha1(name : location : date of birth) 1?". Clearly you'll have tons of collisions with that solution, as you would have with any solution using 33 independent questions. To uniquely identify people, we'd either need to us…

> Clearly you'll have tons of collisions with that solution Why? If we assume the hash code assignment to one of the 2^32 people is uniformly random from a set of 2^160 codes, the odds of finding a collision are astronomically small (order of 2^-95 or so). Am I missing something?

You are not taking the entire hash, you are only taking the first 33 bits of the hash. Since there are only about 8.5 billion different values for the 33 bits and there are about 7 billion people, the odds are astronomically low that each of those 7 billion people will receive a different one of those 8.5 billion possibilities.

This is the birthday paradox with instead of 365 days you have 2^33 possible answer values and instead of 23 people you have 7 billion people. I leave it as an exercise for the reader to fill in these values into one of the formulas to calculate the probability of successfully giving each person a unique 33 bit answer: http://en.wikipedia.org/wiki/Birthday_problem

Re: 33 Questions

#120

Post by jules »

abentspoon wrote: post #69

It's not enough to find 33 independent questions that evenly split the world's population. An optimal, though inelegant solution to that goal might look something like this: "Is the {1..33}th bit of sha1(name : location : date of birth) 1?". Clearly you'll have tons of collisions with that solution, as you would have with any solution using 33 independent questions. To uniquely identify people, we'd either need to us…

It is interesting to see your comment way down the thread, even though it is by far the best.
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