user: Question: What's the percentage of undecided according to the poll source with sampling error of 2.7%?
Columns: ['Poll source', 'Dates administered', 'Tom Emmer (R)', 'Matt Entenza (DFL)', 'Tom Horner (I)', 'Undecided', 'Sampling error']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Survey USA', 'August 2-4, 2010', '33%', '38%', '12%', '17%', '2.7%']
SQL:

assistant: SELECT "Undecided" FROM "Table" WHERE "Sampling error" = '2.7%';