# The Birthday Paradox - let's test it

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I know you didn't name it. It'd be named the Birthday McBirthday Face if someone on the internet named it.

My beef is with it being called a paradox. A logical thinker wouldn't think that because it'd be illogical. The math itself shows that. The whole premise is that this is logical. It's a thing one might not expect at first blush but makes sense after some thought, but it's not a paradox.

Google def of Paradox: "a seemingly absurd or self-contradictory statement or proposition that when investigated or explained may prove to be well founded or true."

So you may not like it being called a paradox, but based on the definition above, I think it fits.

Out of more than six billion people, we're testing to see if a number of them share a very finite commonality; were more than one of them born on one of 365 days, and it's not even a preference. It's not something we could change our minds about due to external or internal influences. I was born the day my body came out of someone else's body. That's it. It's a done deal. And it's to see if one person will share a birthday with at least one other. It's not to see if two people were born on one specific day, say, 1/1/84. No, it's to see if any day, regardless of year, is shared. The constraints are very loose. That's another reason it works like it does. The whole thing is set up to work like it does. That is not a paradox.

Yes, it is, and I am not sure you truly understand it because you're fixated on six billion people. The number of people has nothing whatsoever to do with it. It's simply this: assuming birthdays are random, how many people would you have to randomly pick before there's more than a 50 percent chance two of them share the same birthday. Population size is not important.

In one sense, it's similar to how a polling firm like Gallup can survey just 2400 people out of a population north of 200 million (excluding children), and produce accurate assessments of what everyone is or does or thinks.

But we don't have to rely on me. There are websites after websites which explain why this is not a paradox.

We'll have to agree to disagree on this one. I think it fits the definition, you don't, let's just RDWHAHB.

That said, it isn't seemingly absurd or self-contradictory to me, but I see a lot of people for whom it is.

May 19

...apparently May has not been good to homebrewers?

Well I just changed that

April 30

June 12

November 6

Feb 23

August 8

April 22

Remember remember the 5th of November. Because it's my birthday.

November 8

October 12
big 5-0 today

November 27

April 29th

05/05

October 5

October 16

February 06

9/11

1/31

11/17

6/26

01/01

New Years baby in the house.

12/31

3/2

10/29

OP, I find it interesting that it took so long for a May birth month. Have you looked at the statistics on that? The odds of 1 person not being born in May is .91% (or 334 other days of the year -365) so to get to 67 before a May birthday is 99.7% ... that's pretty impressive.

May 19

I find the those statistics quite intriguing.
My son and I share the same birthday. It seems to follow similar statistics, and apparently is not all that rare.

october 10

i remember going through this problem in college as well. professor ran through the math and then suggested we test the theory by going around the room any listing our birthdays. it was a small discussion class, maybe only 20 students. i was in the front corner so went first...dude next to me had the same birthday. :fro:

My Dad's birthday is October 8th, mine is the 16th, and my sister's is the 23rd. My Mom says she was trying to get one of us to arrive on his birthday. I think it was just cold in February!

June 30

August 12

11/2

May 28

3/26

April 2