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  #1  
Old 31st August 2007, 12:18 PM
FredSpringer FredSpringer is offline
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Database Skew

If a global database has a disproportionate sampling among the countries in its database, isn't the data skewed towards the countries with the larger amount of participants?
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  #2  
Old 31st August 2007, 12:44 PM
MMaddi MMaddi is offline
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The answer to that question is obviously yes. Since the British Isles is the ancestry of most Americans and probably even more so most of those involved in genealogy, FTDNA's database is heavily skewed toward the British Isles. I think that the reason the genealogy community is probably skewed even more so toward the British Isles is that it's easier to do research on a family tree when your ancestors have been in the U.S. for 200 or more years, which is the case with many of those with British Isles ancestry. You have easy access to the records of your ancestors and don't need to know a foreign language to read it. Plus, once you have traced your lines back to their immigration to the U.S., when you research records from the "old country," they're still in English.

The other factor in the FTDNA database is that a lot of the early genetic genealogists were of Jewish ancestry and attracted to DNA testing by the discovery of the Cohen modal in J1/J2.

Many people who can trace their ancestry back 200 or more years to a non-British Isles European country, end up matching most people from the British Isles in FTDNA's database. That's my situation. I can trace my yDNA line back to 1845 in Sicily, but I still have many fairly close matches to those with British Isles ancestry. Part of the reason for that is that I'm R1b. Also, many people note that their matches cite Ashkenazi Jewish ancestry. That's also a result of the skewed nature of FTDNA's database - it doesn't indicate that everyone who matches Ashkenazi Jews is Jewish themselves.

This is not even considering that few people with ancestry outside Europe have tested their DNA at FTDNA. Think of what the database would be like if more Indians and Chinese and Africans tested at FTDNA.
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  #3  
Old 31st August 2007, 12:59 PM
josh w. josh w. is offline
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On the plus side people from the British Isles or of Jewish ancestry are more likely to find matches at FTDNA. I have expressed concern about this problem since joining the forum. The only solution I can see is for there to be a consortium of all public and private data collection endeavors which would identify all anonymous matches by nationality and ethnicity. The problem of selectivity affects all databases not just FTDNA. However this problem can be reduced by combining databases.
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  #4  
Old 31st August 2007, 04:22 PM
vineviz vineviz is offline
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Quote:
Originally Posted by josh w.
On the plus side people from the British Isles or of Jewish ancestry are more likely to find matches at FTDNA. I have expressed concern about this problem since joining the forum. The only solution I can see is for there to be a consortium of all public and private data collection endeavors which would identify all anonymous matches by nationality and ethnicity. The problem of selectivity affects all databases not just FTDNA. However this problem can be reduced by combining databases.
ySearch and mitosearch already act as aggregators in just the way you suggest, yet it is still far from representative. The bias at work is a selection bias: some groups of folks are more likely to be willing and able to undertake DNA tests than other groups.

Unless a third party (like Genographic or an academic study) designs and implements the testing, no amount of aggregation will solve the problem.
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  #5  
Old 31st August 2007, 07:17 PM
josh w. josh w. is offline
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I agree that there needs to be some effort beyond current structures. (Y Search and Mitosearch are essentially tied to FTDNA). I am hoping that the various endeavors would get together for the benefit of their clients or the general public, but I am not optimistic. An independent third party would need the cooperation of all research projects.
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  #6  
Old 31st August 2007, 08:44 PM
vineviz vineviz is offline
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Quote:
Originally Posted by josh w.
I agree that there needs to be some effort beyond current structures. (Y Search and Mitosearch are essentially tied to FTDNA). I am hoping that the various endeavors would get together for the benefit of their clients or the general public, but I am not optimistic. An independent third party would need the cooperation of all research projects.
If by "tied" you mean "funded, hosted, and operated by" then yes.

But, seriously, you've got two huge, free databases with no ads and very little spam that are professionally hosted and virtually never have access problems (downtime, lost data, etc.). Anyone can use the databases with no strings attached and (for searching purposes, without even registering), and ysearch allows the use of dozens of markers that FTDNA does not even offer.

What more do we "need", exactly?
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  #7  
Old 1st September 2007, 04:44 PM
josh w. josh w. is offline
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The two databases do not provide very good coverage because they rely on voluntary choices---many people do not upload. In addition most people who participate do seem to be FTDNA patrons.
I had in mind one central database listing anyone who has ever been tested anywhere. This would require more professional cooperation than can be expected, i.e. it would require the sharing of private databases. Subjects would be identified by background as well as by institution doing the testing. Anyone who has their dna tested would automatically be provided with match results from this anonymous database. It would be useful for "deep" ancestry rather than for recent genealogy.
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  #8  
Old 1st September 2007, 07:11 PM
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Jim Denning Jim Denning is offline
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Quote:
Originally Posted by FredSpringer
If a global database has a disproportionate sampling among the countries in its database, isn't the data skewed towards the countries with the larger amount of participants?

you are what you are
you match what you match reguardless of skewed
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