Geneaolgy Research - Probabilty of Someone having the same name

[berksted]

I never posted in this forum, so if this questions is not relevant, please let me know. I have a family member trying to trace the biological father of my adopted grandfather. From his adoption records she has been able to find a person who matches his name - first, middle and last as well as the same birthday. The last name is Smith so it's common but this was also Minnesota in 1907 (population not too large). I think we have found the right person, but what are the odds of someone having the same name and birth date in a given year.

Since some names are more common that others, I realize this is difficult problem to actually compute, but how does one think about this type of probability?

 

[CRGreathouse]

It's a hard problem because names aren't independent. A "Smith" is more likely to be a "Lawrence" than a "Maurice" (though they're of similar popularity in the overall population).

Toward a first approximation, since Smith is a popular name, I would check records (whatever you can find... SS death records if nothing else, though use a later date in that case) to see what percentage of Smiths in Minnesota have a matching first name and what percentage have a missing last name. Multiply those probabilities together then by the number of people in your database (hopefully not the same one you used to get the percentages) to get a rough first guess of how many matches you'd expect through chance alone. If it's small, there's a good chance that's the one.

 

[zli034]

Randomly pick 6 people from the street. The probability for at least 3 of them have same name or at least 3 of them have different name equals to 1.

 

[jhonpeterson]

This is common problem, I read some other threads & this is so interesting, if anyone who is know more about it so please reply, and I found such useful http://www.kinematik.com/" for researchers & developers.

 

[blue_raver22]

I can understand the importance of genealogy research and the desire to find accurate information about one's ancestors. In this case, it seems that your family member has found a potential match for your adopted grandfather's biological father based on his name and birth date. However, as you mentioned, the last name Smith is quite common and the same birth date may also be shared by others in the same location and time period.

In terms of calculating the probability of someone having the same name and birth date in a given year, it is indeed a difficult problem to accurately compute. This is because it would require data on the frequency of each name in a specific location and time period, which may not be readily available. Additionally, factors such as marriages, name changes, and immigration can also impact the likelihood of someone having the same name and birth date.

However, we can approach this probability by thinking about it in terms of the population size and the likelihood of someone having a specific name and birth date combination. For example, if we assume that the population of Minnesota in 1907 was 2 million and the frequency of the name "Smith" was 1 in every 100 people, then the probability of someone having the same name would be 1 in 100. Similarly, if we assume that the frequency of the specific birth date was 1 in every 365 people, then the probability of someone having the same birth date would be 1 in 365. Multiplying these two probabilities together would give us an estimated probability of 1 in 36,500 for someone having the same name and birth date in a given year.

Of course, this is just a rough estimate and the actual probability may vary depending on various factors. It is also important to keep in mind that this calculation assumes that the name and birth date are independent of each other, which may not always be the case. Nevertheless, it can provide a general idea of the likelihood of finding a match based on these two factors.

In conclusion, while it may be difficult to accurately calculate the probability of someone having the same name and birth date in a given year, we can approach it by considering the population size and the likelihood of each factor. I wish your family member success in their genealogy research and hope that they are able to find the information they are looking for.