When is your birthday?

Glossing over some of the bile that has been posted in this thread... you have touched on a subject that I find fascinating. Do you know about the Birthday Paradox? It is a wonderful thing in mathematics. 

The paradox states that in a random group of 23 people, there is about a 50 percent chance that two people have the same birthday. How cool is that!? It's really not intuitive which is why it is called a paradox.

If anyone is interested in the reasons why this is the case, here you go:

The issue at hand is about comparing birthdays across 23 people. A person's birthday is 1 out of 365 possibilities (forget leap years for simplicity). What's the probability a person does NOT have the same birthday as another person? That is 364/365 - because there are 364 days that are not a person's birthday. So, any two people being compared have a 364/365 (98.7%) chance of not matching birthdays.

The next step is the really cool bit. In any group of 23 people there are 253 comparisons that must be made to check for matching birthdays. Why? The first person to check needs to check 22 people. The next person then needs to check just 21 because the 2nd person was already compared to the first person. And so on. So, you get a sum of 22+21+20+...+1 = 253. So there are 253 chances for matching birthdays in this group of 23.

Every one of these 253 chances as the same probability of NOT being a birthday match. So we multiple 99.7% by 99.7% 253 times this gets you a 49.952% chance that all 253 comparisons have no birthday matches. Therefore, the chance of a birthday match in that group is 1 minus 49.952% which is 50.048% i.e. around 50-50!!!

I find this amazing every time I think about it.

That's what I was getting at personally s couple have over reacted as I stated it's an autistic trait not somone fishing for information. My mate use to be able to memorize the hole school years dates and birthdays he'd ask because he likes to memorize stats and statistics. I also don't think the people who are suspicious are being mean either there probably just not comfortable with sharing personal information. Bare in mind were more or less all on the spectrum here so some of us will react differently to do different topics.

That's what I was getting at personally s couple have over reacted as I stated it's an autistic trait not somone fishing for information. My mate use to be able to memorize the hole school years dates and birthdays he'd ask because he likes to memorize stats and statistics. I also don't think the people who are suspicious are being mean either there probably just not comfortable with sharing personal information. Bare in mind were more or less all on the spectrum here so some of us will react differently to do different topics.