The statistic formed by dividing our estimate of b 2 − b 1 by its estimated standard error: is called the t-statistic. Now notice that we have more than two pollsters. We can also test for pollster...

The statistic formed by dividing our estimate of b₂
− b₁
by its estimated standard error:

is called the t-statistic. Now notice that we have more than two pollsters. We can also test for pollster effect using all pollsters, not just two. The idea is to compare the variability across polls to variability within polls. We can actually construct statistics to test for effects and approximate their distribution. The area of statistics that does this is called Analysis of Variance or ANOVA. We do not cover it here, but ANOVA provides a very useful set of tools to answer questions such as: is there a pollster effect?