> to combine multiple polls to increase the effective sample size and shrink confidence intervals
How does this work? I was under the impression that to shrink the confidence interval by half you need 4x as many sample points, but there must be more sophisticated statistical methods at work here.
His models have a memory (increase sample size by using a handful of day or week old data) and aggregate as many as 5 to 8 independent polls per state plus as many as a dozen national polls that factor into his simulations. That's easily four to sixteen times the sample size.
You can improve effective sample size by eliminating extraneous variables. One thing that Nate does is take advantage of implicit biases (for example, PPP polls lean slightly left)
How does this work? I was under the impression that to shrink the confidence interval by half you need 4x as many sample points, but there must be more sophisticated statistical methods at work here.