Incorrect data found at Find A Grave Sarah was born in 1762. She passed away in 1832. 
Addendum: both find a graves have now been merged see new update showing gravestone with dates of birth and death.
↑"New Hampshire Birth Records, Early to 1900", database with images, FamilySearch: 12 December 2014, Sarah Knowlton, 26 Aug 1764; citing New Ipswich, Hillsborough, New Hampshire, United States, Bureau of Vital Records and Health Statistics, Concord; FHL microfilm 1,001,012.
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It may be possible to confirm family relationships with Sarah by comparing test results with other carriers of her mitochondrial DNA.
However, there are no known mtDNA test-takers in her direct maternal line.
It is likely that these autosomal DNA test-takers will share DNA with Sarah: