Some seeming coincidences are not actually all that unlikely. One I've always liked is that if there are 50 folks in a room, the odds are better than 50:50 that two of them have the same birthday. I told this to a class of 60 engineering students one time and it turned out that two of the students had the same birthday as mine.

We can try it on this forum which must have more than 50 regular viewers. My birthday is July 29.

I've heard that, too, even though there are 365+ days in a year...
October 16.

Actually, for 50 people, the odds are quite a bit better than 50:50 - the probability of two people out of 50 having the same birthday is around 97% !

See: http://en.wikipedia.org/wiki/Birthday_paradox

wasn't it Homer Simpson that said something like... '28% of the people know that 52% of statistics are made up on the spot'.......?

Talking of odd occurances.... when I was younger we went on a holiday to the south of France..... after a nice 2 week break we headed back to England, stopping in shortly at a petrol station to fill up...... who should pull up next to us in the car but my best friend from school who lived only half a mile away from me, 600 miles away back at home!...... now thats gotta be some crazy odds!

That's happened thrice to me.
Once, on vacation from CT in FL (at DisneyWorld), I came across the truck driver for one of our suppliers back in CT; another time, at a party in CA, I came across a gal who was a year behind me in HS in CT; the most recent time, I found that the back neighbor where I was living in NM used to ride with me on the school bus back in CT.
Weird stuff.
In reality, I think that many people we know from different areas, and different times of our lives, pass us all the time, and only once in a while do we become aware of it. Think of all the people passing us on the highways, or on airplanes, etc.

Some of the travel coincidences are not as far-fetched as we might think. I kept running into the same people during a long backpacking trip overseas, and then it finally dawned on me: We were all from the same socio-economic class in the same country, with the same vacation goals, and generally picked up the same guidebook that suggested the same hotels and sights. Any given country can be hundreds or thousands or miles wide, but let's face it, 95% of the middle-class tourists are going to go to the same few roads, trains, hotels, ATMs, and attractions. After that, the only odds left to calculate is the timing.

We may simply not be aware of the actual constraints that narrow the odds in our lives.

The odds in the other direction have to do with all the people I will not encounter simply because their class, religion, interests, and society will cause them to have living patterns that will rarely, if ever, intersect with mine, even if we live in the same town our whole lives.

Doing my homework (instead of trusting my memory) the probability of two people having the same birthday reaches 50.7297% when there are 23 people present. If there are 87 folks present, the probability that three will have the same birthday is 49.9455%. If there are 187 folks available then the probability is 50.2685% that 4 will have the same birthdate, and 5 coincidences requires 313 for a 50.1070% chance of a match.

In summary, for 50:50 coincident birthdays the numbers are: 23 for 2, 87 for 3, 187 for 4, and 313 for 5.

[from: http://www.mathcad.com/library/Libra...8/soln28.html]