How the AP-GfK poll on Clinton and Sanders was conducted

The Associated Press-GfK poll on the Democratic presidential candidates was conducted by GfK Public Affairs and Corporate Communications Feb. 11-15.

No more than 1 time in 20 should chance variations in the sample cause the results to vary by more than plus or minus 3.4 percentage points from the answers that would be obtained if all adults in the U.S. were polled.