From Mark at Larvartus Prodeo:
As Christian Kerr wrote yesterday, the important thing to watch in the polls is the trend, not individual surveys.
No. Definitely not. If polls are measured with a lot of error (and we know they are), then the difference between two polls will be measured with even more error. The upshot is that a news outlet that tells us “Labor isÂ down 2% in the polls this week” is about as useful as a weather report that says “the chance of rain today is 10% higher than yesterday”.Â
Here’s Simon Jackman on the topic:
Two polls with sample sizes of about 1,500 each have about a 50-50 shot at finding statistically significant changes when the real change is 4 percentage points, and it only gets worse for smaller changes in vote share. By the way, four percentage points is a lot of change, relative to the variation in actual vote shares in Australian electoral history.
My last post on the topic.