NBC-WSJ-Marist published the results of a new poll. In this poll, interviewees from Pennsylvania were asked for whom they will vote: Republican Donald Trump or Democrat Hillary Clinton.
NBC-WSJ-Marist poll results
Of those who answered the question, 48.0% said that they will vote for former New York Senator Hillary Clinton, whereas 37.0% said that they would give their vote to real estate developer Donald Trump.
The poll was carried out from August 3 to August 7 with 834 registered voters. Considering the poll's error margin of +/-3.4 percentage points, the gap between both candidates is statistically significant.
Putting the results in context
As a general rule, however, you should not have too much faith in the results of single polls, as they often incorporate large errors. At the very least, one should examine how a poll's results compare to benchmark forecasts.
In order to make the results comparable to forecasts from other methods, you can translate them into shares of the two-party vote. This yields figures of 56.5% for Clinton and 43.5% for Trump.
Comparison to other polls
If we look at an average of Pennsylvania polls, Clinton's current two-party vote share is at 55.2%. In comparison to her numbers in the NBC-WSJ-Marist poll Clinton's poll average is 1.3 percentage points worse. This deviation is within the poll's error margin, which means that the poll is not an outlier.
The poll in comparison with PollyVote's forecast
The current PollyVote foresees Clinton to gain 53.4% of the two-party vote in Pennsylvania. That is, Polly's prediction is 3.1 points below her polling numbers. The PollyVote forecast is thus within the poll's margin of error.