UPDATE: Pollster and professor Matt Barreto takes issue with my characterization that the spread between Rob McKenna and Jay Inslee is not statistically significant. I applied the margin of error – 3.2 percent – to both candidates’ results. That is, I add that number to Inslee’s result and subtract it from McKenna’s. That is the common practice to determine whether the difference between the two in the poll is significant.
But it is not the only way and Barreto maintains that I also need to look at the probability of the poll.
“The poll results reveal a 92.3 probability that the McKenna lead is real, and a 7.7 percent probability that it is a not real,” Barreto wrote.
While there is overlap between the two results based on the margin of error, such an occurrence is only probable 7.7 percent of the time. Therefore , statistically, the difference between the two candidates is considered significant.
The question came up after it was pointed out that the Washington Poll’s press release contained incorrect numbers for McKenna and Inslee that indicated an even-wider margin between the two. Barreto blamed the mistake on a typo and said that both the incorrect and the correct numbers are still significant.
Here is the original post (with strikeovers showing the incorrect and the corrected numbers).
In its first look at the potential 2012 matchups for Washington governor and U.S. president, the Washington Poll has state Attorney General Rob McKenna leading likely Democratic rival U.S. Rep. Jay Inslee.
It also has President Barack Obama ahead in Washington state over former Massachusetts Gov. Mitt Romney and Texas Gov. Rick Perry.
Of those surveyed,
45 percent 43.9 percent said they would vote for McKenna in the open race for governor. Inslee was supported by nearly 38 38.4 percent. That difference is not outside the polls margin of error and is considered by pollsters to not be statistically significant.
Two possible presidential matchups were tested: Obama leads Romney 50-41 and leads Perry 54-41. When asked whether they had confidence in Obama or the Republicans, 41 percent of voters said Obama and 37 percent said Republicans.
Pollsters interviewed 938 registered voters between Oct. 10 and 30 and used both land-line telephone and cell phones. The margin of error is 3 percentage points. The Washington Poll is administered at the University of Washington Center for Survey Research and directed by Matt Barreto, an associate professor of political science
Here is a link to the entire poll.