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Friday, June 29, 2018

AncestryDNA Shared Match Quiz: Results

Have you tried the AncestryDNA Shared Match Quiz? If not, give it a go. The results will still be here when you come back.

If it made your head spin, don’t despair. You were not alone.

Total score

As at this morning, there were 812 valid responses to the quiz. Of these, 465 scored less than 5/10. Only 13 responses scored full marks. It appears I’m a tough quizmaster.

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Results by question

Questions 1 to 5 considered shared matches with an estimated 4th or closer cousin. The questions were:

Betty is your estimated "3rd to 4th" cousin and shares 153cM with you. When you view her match page, you see three shared matches.

1. How many matches do you and Betty share in total? That is, how many people who appear anywhere in your full match list also appear anywhere in Betty's full match list?

2. Of the three shared matches on Betty's match page, how many share at least 20cM with you?

3. Of the three shared matches on Betty's match page, how many share at least 20cM with Betty?

4. Betty logs into her account and looks at your match page. How many shared matches does Betty see?

5. Betty logs into her account and looks at your match page. How many of them are the same people you see?

These were intended to be the easiest questions, and the results showed that generally speaking they were. Even so, only around 60% of respondents answered question 1 correctly. Question 1 tested if the respondent knew that there was a limit on the shared matches shown, without requiring knowledge of what the limit was. That’s around 40% who did not provide a correct answer.

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Questions 6 to 10 looked at shared matches with a distant relative and his daughter. The preliminary instructions said to assume that the shared DNA estimates are accurate and that the trees involved don't have intermarriage or additional coincidental relationships.

John is your estimated "5th to 8th" cousin (actually a 6th cousin). He shares 8.3cM with you. On his match page you can see five shared matches.

6. How much DNA does the most distant of those five matches share with you?

John's daughter, Jane, has also DNA tested with Ancestry. As his daughter, she is John's closest match. Jane is a DNA match to you. 

7. Still thinking about your view of John's match page, assess this statement: Jane is the top entry in John's shared match list with you.

8. You see Betty (your third cousin, shares 153cM) when you look at John's (your 6th cousin, shares 8.3cM) shared match list with you. How much DNA does John share with Betty?

9. If Betty logged in to her account and looked at YOUR match page, would she see John in the shared match list?

10. If Betty then navigated to John's match page, would she see you in the shared match list?

Question 6 required application of the knowledge that there’s a threshold. Questions 7 and 8 required application of that knowledge together with the concept that while a threshold includes some relationships, it excludes others. Questions 9 and 10 were intended to be the most difficult as they took the same scenarios but considered them from the point of view of the DNA match. Overall, questions 7 to 10 had a lower share of correct answers submitted, at around 25% for each question.

I was curious to see which questions tripped up people with high scores. The results below are only for responses that scored 7, 8 or 9.

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I had expected question 9 or 10 to cause the most problems, but question 7 won that prize. To answer correctly, respondents needed to know that if two matches were distant to them, they would not see a shared relationship between the two distant matches, no matter how closely related the two distant matches were to each other.

I wrote this questions because I’ve come across a similar situation – and been confused by it! – when working with my own matches. The situation I faced was identical twins who didn’t show up as shared matches. The reason seems obvious to me now, but had me scratching my head at the time.

I plan on leaving the quiz open indefinitely, so if you ever wish to go back and try again it will be there.