NBC-WSJ-Marist released the results of a new poll, in which respondents from Pennsylvania were asked for whom they will vote: Republican Donald Trump or Democrat Hillary Clinton.
NBC-WSJ-Marist poll results
The results show that 48.0% of interviewees intend to cast a ballot for former Secretary of State Hillary Clinton, whereas 37.0% plan to vote for billionaire Donald Trump.
This poll was conducted from August 3 to August 7, among a random sample of 834 registered voters. There is a sampling error of +/-3.4 percentage points. Considering this error margin, the gap between both candidates is statistically significant.
Putting the results in context
As a general rule, however, a good strategy is to not have too much faith in the results of single polls, since they sometimes incorporate large errors. Rather than relying on results from single polls, forecasting research recommends to consult combined polls or, even better, the combined PollyVote forecast that relies on different methods and data.
In order to make the results comparable to benchmark forecasts, one can convert them into two-party vote shares. The corresponding figures are 56.5% for Clinton and 43.5% for Trump. For comparison: Only 55.6% was gained by Clinton in the NBC-WSJ-Marist poll on August 1, for Trump this result was 44.4%.
Comparison to other polls
If we look at an average of Pennsylvania polls, Clinton's two-party vote share is currently at 55.2%. Compared to her numbers in the NBC-WSJ-Marist poll Clinton's poll average is 1.3 percentage points lower. This deviation is within the poll's sampling error, which means that the poll is not an outlier.
The poll compared with PollyVote's prediction
The latest PollyVote forecasts Clinton to gain 53.3% of the two-party vote in Pennsylvania. This means that Polly's combined forecast is 3.2 points below her polling numbers. The PollyVote forecast is therefore in line with the poll's error margin.