I share the same birthdate as my boyfriend, same date but also same year, our births are seperated by merely 5 hours or so. I know that the chances of meeting someone who was born on the same date than me is fairly high and I know a few people with whom I share my birthday although for the little I've read about the birthday paradox, it doesn't take same year into account.
We've argued before about the probabilities and I am still not satisfied. I find the amount of factors to take into account quite vast up to a point, gender and age, availability, probabilities of separation in our region, etc. Is it even possible to calculate the probabilities on something like this?
How would you go about it?
For any one relationship, the odds of sharing the same month and day are approximately 1 in not exactly because of leap year and because births are not exactly evenly spaced within a year. If you add in year, it's probably something like 1 in or most people have relationships with people relatively close in age.
That is, if you had asked, before meeting your current boyfriend "What are the odds that the next man I have a relationship with will be born on same day and year? However, post hoc that is, while in the relationship it's trickier because you would have noticed a lot of other coincidences too: My boyfriend was born the day before me! My boyfriend's mother has the same name as my mother!
Your question got me thinking, and I realized my girlfriend and I also have a strange birthday coincidence.
She was born exactly days before me! And we are also in a successful relationship! So, first of all, the odds of sharing some weird connection with any random person are probably quite high.
Next one should figure out what the chance is of being born in the same year. However, the chances of dating someone from the exact same year are far greater due to a flaw in the educational system where pooling is done by the date of conception. What that exactly boils down to depends on age and month born, but for me it boiled down to more than 0.
Definitely not normal, but then again, coming full circle, you will find something like that for everyone after the fact. The chance that your boyfriend was born the same year as you is actually very high especially given many situations tend to bring people of very similar age together ; it's a very difficult probability to calculate, though, without data.
But P same day should be roughly independent of whether you were born in the same year. So if you had some good estimate of P Same year , you can calculate the overall probability reasonably well. I'd guess that P same year is roughly of the order of 0. According to wikipedia , Thus, a baseline estimate for sharing the same date of birth would be the above statistic divided by two because it captures 2 years for sharing the same year multiplied by the probability of sharing the same birthday:.
As has been noted, both the shared year and shared birthday probabilities could be further refined based on additional information.
When it comes to two people, there are many potential sources of coincidences. Humans are very good at identifying patterns. Within the domain of date of births, you could imagine many possible similarities: same month; same day of month; same star sign; same birthday, different year; some similarity in the numbers such as 2nd of May and 5th of February; dates are some round number apart e. We could in some sense describe our sense to which any of these feel surprising or like a major coincidence.
But of course, when we speak about coincidences there is a much wide domain of search. For example, we could look at similarities in names, employment history, appearance, etc.
The larger you cast the search, the more possible bases there are for finding coincidences. In general, the more you look for them, the more you will see them. This is analogous to the analyst who performs many post-hoc statistical tests without correcting alpha. With enough analyses, the probability of finding a significant pattern gets close to one even when alpha is small. Although the question is about birthdays, the "birthday paradox" isn't really relevant here.
It's about how many random samples you need to take before you expect at least two samples among them to be equal a collision.
Your question is mostly about the probability of two samples being equal. If there were 30 people in your relationship then you'd expect two of them to share a birthday but there aren't 30 people, there are only 2. The odds of having a relationship only have quite a small effect. Enter your birth date and discover what day you were born on and how long you've been alive. In addition, find out your star sign, chinese zodiac sign, celebrities you share your birthday with and your no1 chart song.
If you like my calculator, please help me spread the word by sharing it with your friends or on your website or blog. Thank you. Whilst every effort has been made in building this birthday calculator, we are not to be held liable for any special, incidental, indirect or consequential damages or monetary losses of any kind arising out of or in connection with the use of the converter tools and information derived from the web site.
This birthday calculator is here purely as a service to you, please use it at your own risk. Do not use calculations for anything where loss of life, money, property, etc could result from inaccurate conversions. Please see the full disclaimer for more information. As with all of the calculators on my website, I love to receive suggestions for additional features.
grunadecle.tk So, if you would like to see any new features added to this birthday calculator, please contact me.