On October 19, NBC-WSJ-Marist released the results of a new poll, in which respondents from Arizona were asked for whom they will vote: Democrat Hillary Clinton or Republican Donald Trump.
NBC-WSJ-Marist poll results
The results show that 41.0% of participants said that they would give their vote to former New York Senator Hillary Clinton, whereas 42.0% are going to vote for billionaire Donald Trump.
The poll was carried out from September 6 to September 8 with 649 likely voters. There is a sampling error of +/-3.8 percentage points. Considering this error margin, the race is currently a statistical tie.
Putting the results in context
As any other method, polls are subject to bias. Thus, as a general rule, you should not be too confident the results of an individual poll. Rather than trusting the results from single polls, the best practice is to consult combined polls or, even better, the combined PollyVote forecast that includes forecasts from different methods, each of which includes different data.
For the following comparison, we convert Clinton's and Trump's raw poll numbers into two-party vote shares. This procedure yields values of 49.4% for Clinton and 50.6% for Trump.
Comparison to other polls
An average of recent polls in Arizona sees Trump at 49.1% of the two-party vote. Compared to her numbers in the NBC-WSJ-Marist poll Trump's poll average is 1.5 percentage points lower. This difference is within the poll's error margin, which suggests that the poll is not an outlier.
The poll compared with PollyVote's forecast
The latest PollyVote predicts Trump to gain 51.3% of the two-party vote in Arizona. This means that Polly's combined forecast is 0.7 points above her polling numbers. The PollyVote forecast is therefore in line with the poll's margin of error.