Simple Explanation of the Birthday Paradox

[@WrathofMath]

Please ignore my inclusion of the /yy early in the video, we aren't considering year - only day and month. Professional silly goose over here. More math chats: kzbin.info/aero/PLztBpqftvzxXQDmPmSOwXSU9vOHgty1RO Join Wrath of Math to get early&exclusive videos, lecture notes, music, and more! kzbin.info/door/yEKvaxi8mt9FMc62MHcliwjoin

[@jonnomonodesu]

You included 'yy' in the example so the calculation would be completely different as you would have to include the odds of the year being the same which changes the problem. The video only covers the dd/mm calculation.

[@WrathofMath]

very silly oversight! Thankfully we didn't spend too much time with the mm/dd/yy, so hopefully it won't cause confusion

[@Mikemenn]

Yeah, the yy is throwing this things off

[@IvanToshkov]

Once at a party some lady was explaining how certain dates seem to be "special," because important events happened on them. I told them about this paradox and showed that just 23 events will be enough to make it more likely to have such collisions. And it's not that hard to come up with important events. I haven't been asked on such parties since.

[@mattsadventureswithart5764]

Using maths or facts to show that superstitious stuff is nonsense appears to upset people. I have no idea why.

[@IvanToshkov]

@@mattsadventureswithart5764 It's bad luck, that why! :D

[@Drogobo]

this actually happened multiple times in my elementary school

[@WrathofMath]

It did in mine as well because there were twins in my class haha. Eventually they left, and by senior year my graduating class was I think 27 people strong with 27 distinct birthdays.

[@NoNowwwell]

Nice Mario 64 penguin world music.

[@thatoneginger]

When you said 23 factors you weren’t totally wrong; it’s just the first factor is the probability that the first guy doesn’t share a birthday with anyone previous, which is 365/365, or 1

[@WrathofMath]

Yeah, I only put the correction because in the video I was specifically discussing factors less than 1. A minor slip of the tongue!

[@robertveith6383]

*@ Wrath of Math* -- You could do the calculations for us for the number of people in the room where three people and four people share a birthday, and that it is likely.

[@russellstyles5381]

Most people incorrectly think about how many people it takes for 2 of them to be more likely (> 50%) to have A specific birthday, eg Dec 27. That's not the question.

[@gpcm]

I love when mathematicians can explain their concepts with simple logic

[@balrog240]

Great job, best explanation I've seen to date

[@WrathofMath]

Thank you!

[@MellohiYT]

underrated

[@WrathofMath]

out here cooking

[@Moon_Crescent2341OO]

It’s not the answer of people who own a same birthday/the total number of people, it’s that if 2 people in the room have a bruthday it’s gonna be a lot

[@Moon_Crescent2341OO]

2:27 23

[@monoman4083]

very good

[@WrathofMath]

Thank you!

[@hadz8671]

leap years?

[@thomasw.eggers4303]

leap years makes only an insignificant change.

[@Falcon-0-or6vj]

👍

[@Curio_med1a]

I dont understand a single thing, i can barely remember my own birthday 😂😂

[@MegaPhycoKiller]

This question obviously doesn't take into account that people are born more often on certain days. Example, mid October is common because they were conceived on Valentine's Day, December 25th is very uncommon because Christian mothers will deliberately avoid that day and will have the doctors induce an early pregnancy, which bloats the chances of the proceeding days.

[@WrathofMath]

This is true, but it's not super relevant to the problem at hand because that only makes it more likely that a small group of people would have a common birthday. So the 23 number is a worst case scenario so to speak. Assuming uniform distributions of birthdays, it takes 23 people. Accounting for the non uniformity would only increase the odds for 23 people sharing a birthday, and accounting for leap years is an insignificant change that doesn't add anything to the interest of the problem.

[@KarlBonner1982]

Valentine’s Day conceptions are born in November, not October

[@beltanewalk8797]

​@@KarlBonner1982An extremely servere case of premature ejaculation perhaps.

[@russellstyles5381]

If you use standard rounding, it reaches 99.9% at 67 rather than 75, at 99.844%, which rounds off to 99.9%

[@eduardoxenofonte4004]

You can't say it's reached 99.9% if it's less than 99.9%, even if it rounds to 99.9%.

[@ahmadnematov7530]

But i didn't see among my classmates who shares same birthday (24)

[@ignDart]

people when probabilities are probabilities

[@killianobrien2007]

You have failed a coin toss before, right?