Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

33 Questions

github.com

Post reply on HN
Print view View original

151–160 of 169 posts

Re: 33 Questions

#151

Post by upquark »

jules wrote: post #119
upquark wrote: post #95

Earlier quoted context omitted.

> 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…

> You are not taking the entire hash, you are only taking the first 33 bits

Right, my bad, didn't pay attention to the problem we are trying to solve :)

Re: 33 Questions

#152

Post by bazzargh »

deathanatos wrote: post #141
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…

I dislike some of the examples of the "falsehoods programmers believe about time" because they typically aren't falsehoods, and will always hold true within the constraints of your system. Yes, time is a fickle thing that is marred by history, but in building a system, I choose a representation for the data I am storing in it. If I choose to store dates using a Gregorian calendar (because I'm following ISO-8601), the…

2 AM might not repeat in UTC, but midnight does if your internal representation uses unix timestamps (or similar - .Net doesn't count leap second ticks either)

http://en.wikipedia.org/wiki/Unix_time

Re: 33 Questions

#153

Post by Scarblac »

gkoberger wrote: post #8

Very interesting thought experiment. A few random thoughts: Reminds me of Panoptic by the EFF: https://panopticlick.eff.org/ Everyone's ID would change as time passed (if they move, if they age, if they get a sex change, etc). The best questions for this are inherently "irrelevant", since "relevant" questions tend to be statistically linked. So, questions like "Was the second letter of your first girlfriend's middle…

But""Was the second letter of your first girlfriend's middle name between A and M?" is a bad question on many levels -- people who aren't attracted to females, people who are but have never had a girlfriend (including children), people who got married to their wife as the start of the relationship, and cultures where "girlfriend" would be hard to define because of that sort of thing.

I can think of almost perfectly 50/50 questions based on odd/evenness of numbers (is your current weight in grams/age in hours/number of hairs odd or even) but those are completely time dependent.

Re: 33 Questions

#154

Post by sixbrx »

deathanatos wrote: post #141
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…

I dislike some of the examples of the "falsehoods programmers believe about time" because they typically aren't falsehoods, and will always hold true within the constraints of your system. Yes, time is a fickle thing that is marred by history, but in building a system, I choose a representation for the data I am storing in it. If I choose to store dates using a Gregorian calendar (because I'm following ISO-8601), the…

2am doesn't even repeat in the local timezone, it's just that the timezone changes. So here for example, 1:59:59 am CDT increments to 1:00:00 CST, which does not conflict with the earlier 1:00:00 CDT. I think it would be better not to go through all this hassle though, myself.

Re: 33 Questions

#155

Post by ebiester »

k__ wrote: post #149
ronaldx wrote: post #147

Earlier quoted context omitted.

Not really. The stats have not been thoroughly calculated (to my knowledge) but here is an attempt: http://www.isna.org/faq/frequency Not XX and not XY: one in 1,666 births Klinefelter XXY: one in 1,000 births There are other relevant cases, not necessarily measured here, like mosaicisms and chimerism. "Do you self-identify as female?" is a more answerable question.

but doesn't 1:1666 mean the success rate is more than 99%? Asking about the posession of an XX chromosome should separate the people almost 50:50, the rest is something else. On the other hand, maybe there are just <1% people who don't identify them self with being male or female, so the questions would make no difference...

All that matters is that the answer stays consistent for purposes of the 33 questions.

Re: 33 Questions

#156

Post by PeterisP »

deathanatos wrote: post #141
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…

I dislike some of the examples of the "falsehoods programmers believe about time" because they typically aren't falsehoods, and will always hold true within the constraints of your system. Yes, time is a fickle thing that is marred by history, but in building a system, I choose a representation for the data I am storing in it. If I choose to store dates using a Gregorian calendar (because I'm following ISO-8601), the…

If you store time in UTC, then you haven't solved all possible time storage problems - for example, you still need to take into account that some days have 25 hours; so any structures for exchange/storage of periodic data (hourly planning schedules; by-minute temperature readings) need to contain a variable number of data instead of fixed set of 24 hours. If your HR system is doing employee scheduling for 24/7 shifts, then those days may cause a lot of issues no matter how you represent that data.

And the 'display issues' are nontrivial - it's not just converting a timestamp to a string; it has tricky consequences for UI layout and printing if those night hours matter.

Re: 33 Questions

#157

Post by PeterisP »

_sh wrote: post #111
ketralnis wrote: post #106

Earlier quoted context omitted.

> 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.

For the purposes of this problem (and most other purposes) if you have a question that divides answers in 47%:A 51%:B 2%:'stupid_question_doesn't_fit_me_I'll_answer_randomly', then it's still perfectly okay.

Re: 33 Questions

#158

Post by xauronx »

scraplab wrote: post #53
ZirconCode wrote: post #11

Just use: - Birthday (19~ bits) - Rough Location (remaining bits) And base the questions around those two, for example, where you born on a 1-15th, does the city you were born in start with the letter's a-k. This part would be an exercise in statistics, I would think. edit: And one bit for if you were the first to be born of two identical twins =p

Lots of people don't know their birthday, or if they do, it was written down as 1st Jan (or another memorable date), because their parents/carer didn't know when they came to register them, if they ever registered them. There will be bias towards those memorable dates.

"Lots of people don't know their birthday" Really? I've never met a single person who didn't. I guess "lots" in the terms of thousands could be plausible, vs "lots" in the terms of "a high percentage".

Re: 33 Questions

#159

Post by glomph »

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…

Mirror for the gender post: http://pastebin.com/raw.php?i=25bnhuBC

Re: 33 Questions

#160

Post by ludston »

k__ wrote: post #149
ronaldx wrote: post #147

Earlier quoted context omitted.

Not really. The stats have not been thoroughly calculated (to my knowledge) but here is an attempt: http://www.isna.org/faq/frequency Not XX and not XY: one in 1,666 births Klinefelter XXY: one in 1,000 births There are other relevant cases, not necessarily measured here, like mosaicisms and chimerism. "Do you self-identify as female?" is a more answerable question.

but doesn't 1:1666 mean the success rate is more than 99%? Asking about the posession of an XX chromosome should separate the people almost 50:50, the rest is something else. On the other hand, maybe there are just <1% people who don't identify them self with being male or female, so the questions would make no difference...

| On the other hand, maybe there are just Huzzah for logic. But note that the question was, "Do you have 1 apple" and not, "Choose a statement: 'I have 1 apple', 'I have 2 apples'"
Post reply on HN