Comments on: Brain Game: We’re Gonna Have a Party, Party

By: Miss Cellania

Miss Cellania — Sun, 29 Jun 2008 14:11:27 +0000

If I plan for a party of 23 people, it’s a sure bet 100 will show up.

By: Just Al

Just Al — Sat, 28 Jun 2008 16:57:18 +0000

Um, the answer is 2. You said nothing about random people, or not knowing their birthdays.

And fix the Tab problem in the commenting form.

By: Sandy

Sandy — Fri, 27 Jun 2008 23:16:01 +0000

UPDATE: Yes, you folks are correct. I meant to say a 50 percent chance, not 2:1 odds. They’re two quite different things, and it was my bad. I’ve changed the phrasing of the question to make it correct.

Thanks for the heads-up, all!

By: MrTisoy

MrTisoy — Fri, 27 Jun 2008 22:53:23 +0000

I have to agree with Jason, and with Emily. Sandy asked one question but then posted the answer to a different question and linked to how the other question was solved.

The question asked is “how many people are necessary for odds better than 2:1″, which means better than 66.6% (or possibly better than 33.3%, depending on how you look at it.)

The answer (23) is the answer to “how many people are necessary for odds better than 1:1″, which means better than 50% or “even” odds.

The answer to the question asked is 29 (or 18, if you are looking for better than 33%)

Look at the linked “detailed explanation” if you don’t believe me.

By: Patrick

Patrick — Fri, 27 Jun 2008 19:53:22 +0000

Sept 29 here also

By: Patrick

Patrick — Fri, 27 Jun 2008 19:37:40 +0000

This was in an old Scientific American magazine–a one page math problem/example. They used a soccer game (with 23 people on the field, players plus officials) as an example.

By: lindsey

lindsey — Fri, 27 Jun 2008 19:25:26 +0000

so.. i’m september 29th.
any one else?

By: dant

dant — Fri, 27 Jun 2008 18:13:34 +0000

Actually 29 happens to be the minimum number of people for the odds to be better than 9:1! It goes up fast.

By: Humaira

Humaira — Fri, 27 Jun 2008 17:49:41 +0000

23 – we spent an entire class period deriving this in my college Statistics class. And 10 years later, it’s the only thing I retained from that entire semester. What are the odds?!

By: Emily S S

Emily S S — Fri, 27 Jun 2008 17:02:20 +0000

I think it is 29…