Different DNA results on Ancestry and My Heritage??

[Gadget]

I manage my niece's DNA and have been contacted via My Heritage by someone who shares 69 cM over 3 segments. I thought I recalled the name so checked on Ancestry and find that the person is shown there as sharing 47 cM over 3. Exactly the same tree, name. location are used so I'm assuming this is the same person.

I know that different sites do differ slightly in the results produced but this seems a rather large difference and suggests that they are from two different but related people.

Any thoughts


Gadget

[Gadget]

I forgot to say that the original test was via Ancestry. I then uploaded the results to My Heritage. Her results with me are:

Ancestry  1846     My Heritage - 1981

[Mart 'n' Al]

Gadget, what are the respective segment sizes? I'm sure you have considered this but I'm just curious.

Martin

[Gadget]

I've found a few differences with my DNA on the two sites. I think My Heritage uses a different method of calculating shared DNA. These were also using the original Ancestry test results uploaded to My H.

e.gs of some of my relatives that I knew before I did any tests:

a.
My H  133 /7
Anc - 120/6

b.
My H 110/4
Anc 70/6

c.
My H 70/3
A 48/3

[Gadget]

Gadget, what are the respective segment sizes? I'm sure you have considered this but I'm just curious.

Martin

I'm not sure that it makes much difference but this is what they are:

Shared segment sizes -  37; 16.6; 15.6

No way of knowing with Ancestry results.

[Mart 'n' Al]

Are the segments all a good (7cM+) size in each case?

Ships that pass...

Martin

[Gadget]

I think you posted just after me - all are reasonable size.

[Gadget]

I'm betting that all My Heritage matches have higher (and in some cases,  much higher) shared DNA than Ancestry.

[SelDen]

I don’t know if all do, but I can certainly confirm that at least a couple  of mine have larger amounts of matching DNA on MyHeritage than on Ancestry. The one I can remember without checking is around 50CM on MH compared to around 19CM on Ancestry.

I have read that Ancestry seeks to eliminate the ‘background noise’ ie the kind of matching that occurs within a general population.