MPR News/Star Tribune poll: Here's how the poll was conducted

Mason-Dixon Polling & Strategy interviewed 800 registered Minnesota voters from Feb. 17 to 19, using a mix of land lines and cell phones. Of these voters, 37 percent identified as Democrats, 32 percent as Republicans and 31 percent as independents or with other parties.

Just under one-third of voters were from Hennepin and Ramsey counties, while 29 percent came from other suburban counties in the Twin Cities metro area. Southern Minnesota was home to 20 percent of respondents and northern Minnesota to 19 percent. These figures correspond to those areas' share of Minnesota's registered voters.

Around 80 percent of voters shared their household income; of those who did, 11 percent said they earned less than $25,000 per year; 18 percent between $25,000 and $50,000; 17 percent between $50,000 and $75,000; 13 percent between $75,000 and $100,000; and 20 percent $100,000 or more.

Educationally, about half the sample had a college degree or more, and about half had some or no college. Around a quarter of respondents were 65 years old or older, and 17 percent were 18 to 34.

Beyond the 800 voters in the survey's main sample, Mason-Dixon also interviewed extra voters about a subset of the questions to ensure a large enough sample size. A total of 500 voters who intended to vote in the Democratic presidential primary were asked about their preferences for that race, and 500 voters 18-34 were asked questions related to generational issues.

The overall survey has a margin of error of +/- 3.5 percentage points. For example, 44 percent of voters in the survey said they approve of President Donald Trump's job as president. The margin of error means that we can be 95 percent confident that Trump's actual approval with all Minnesota voters lies between 40.5 percent and 47.5 percent, based on how large-enough random samples approximate larger populations.

The 500-voter samples of Democratic primary voters and young voters have a slightly higher margin of error of +/- 4.5 percentage points.

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