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The Birthday Paradox Experiment (2018)

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Re: The Birthday Paradox Experiment (2018)

#41

Post by jyounker »

nuancebydefault wrote: post #22
unklefolk wrote: post #21

Earlier quoted context omitted.

The Birthday Paradox is about a group of people sharing at least one birthday between them. If it was at least 1 person out of 23 people sharing YOUR birthday then the odds would be 1 - (364/365)^23 which is around 0.06 (or 6% chance). So, yes, this scenario is a lot less likely.

Thanks for that. I believe the fact that it asks for a birthday puts people's brain in a mode where the awe at the end is bigger. Related, having flat tires on a car seems to come in little bursts,like 10 years none and then 2 in a year.

I'd expect flats on cars to be correlated. People tend to buy tires in sets, so age related factors affect them all. Similarly they tend to get driven on the same roads, so are subjected to similar environmental damage.

Also, people are good at noticing patterns that don't exist, so that's a possibility too.

Re: The Birthday Paradox Experiment (2018)

#43

Post by nicoco »

tromp wrote: post #42
k__ wrote: post #35

Aren't there birthdays that are more likely than others?

There is one birthday that is far less likely than others, courtesy of leap years. All other are roughly similar, with small seasonal variation.

And no moon cycle related variations, despite a popular (false) belief. It always amazes me that the superstition is spread even among (some, of course not all) midwifes!

Re: The Birthday Paradox Experiment (2018)

#44

Post by xydone »

dustincoates wrote: post #40
xydone wrote: post #37

Earlier quoted context omitted.

Assuming you don't have an automated system to give away locker keys, wouldn't this be explained by the fact that gym front desk is more likely to give out the lowest number available and as you took X, they will give out X+1 for the next person?

I've never been to a gym where you're assigned a locker for the day (or given a key). Either you have one permanently assigned (rare) or you go in and find one that isn't occupied.

Ohh, I see! At my gym, locker keys are given to you by the front desk and you put in something as deposit (such as your gym card or whatever you wish) and on your way out you give the key and you get your deposit back.

Re: The Birthday Paradox Experiment (2018)

#45

Post by lukol »

While the math is clear, I'm a bit annoyed by the label "paradox" as the whole setup is too simplistic and reductionistic.

The actual chance of being in the same room with someone who shares your birthday needs to include other factors like your socioeconomic background, the cultural environment you are in, your present location, and certain historical facts.

Without having done the math, I'm fairly certain that a member of the baby boomer generation in New York has a higher chance of meeting their birthday sibling than a 12-year-old in a rural part of Australia.

Re: The Birthday Paradox Experiment (2018)

#46

Post by wodenokoto »

lukol wrote: post #45

While the math is clear, I'm a bit annoyed by the label "paradox" as the whole setup is too simplistic and reductionistic. The actual chance of being in the same room with someone who shares your birthday needs to include other factors like your socioeconomic background, the cultural environment you are in, your present location, and certain historical facts. Without having done the math, I'm fairly certain that a me…

Wait, what?

Are you saying that income influences what time of the year you are born?

The paradox doesn’t talk about meeting your birthday sibling, but meeting two people who are birthday siblings.

So by the time the 12 year old has met ~20 people, there is a 50/50 chance that amongst those 20, there’s a birthday pair.

Re: The Birthday Paradox Experiment (2018)

#47

Post by tomtom1337 »

lukol wrote: post #45

While the math is clear, I'm a bit annoyed by the label "paradox" as the whole setup is too simplistic and reductionistic. The actual chance of being in the same room with someone who shares your birthday needs to include other factors like your socioeconomic background, the cultural environment you are in, your present location, and certain historical facts. Without having done the math, I'm fairly certain that a me…

Could you explain more what you mean? Other than certain holidays perhaps causing a higher chance of alone time for future mom and dad, I don’t see what you mean, and I don’t understand your last paragraph.

Re: The Birthday Paradox Experiment (2018)

#49

Post by Eddy_Viscosity2 »

xydone wrote: post #44
dustincoates wrote: post #40

Earlier quoted context omitted.

I've never been to a gym where you're assigned a locker for the day (or given a key). Either you have one permanently assigned (rare) or you go in and find one that isn't occupied.

Ohh, I see! At my gym, locker keys are given to you by the front desk and you put in something as deposit (such as your gym card or whatever you wish) and on your way out you give the key and you get your deposit back.

But why? Seems like it would be inconvenient to gym-users to add these extra steps to getting in and out of the gym. Especially if you have to wait behind other people just to get or return a key. What is the benefit of such a system?

Re: The Birthday Paradox Experiment (2018)

#50

Post by emmelaich »

badcppdev wrote: post #38

I was going to say that I was disappointed that the page didn't show the formula for the probability and show how it changes as you change the number of people in the room. Then I checked the wiki page and understood that some of the maths is actually quite fiendish (for non mathematicians anyway) - https://en.wikipedia.org/wiki/Birthday_problem

Also https://matt.might.net/articles/counting-hash-collisions/
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