Friday September 6, 2013
I’m looking to see if I have missed something, but I think thats it. I’ve got the releases yesterday, including the 54-46 results from Newspoll and Nielsen:
Entering all this into the poll averaging model produces an ALP TPP estimate of 46.2%, +/-0.9. The 90-day trajectory (click for larger view):
- the model that is constrained to fit the 2010 election result exactly, and produces a set of house effects that are all positive (i.e., virtually all pollsters overestimated Labor’s 2010 TPP performance), which produces an estimate of 45.7% ALP TPP
- a model that is identified by assuming the house effects sum to zero (i.e., the polling industry is collective unbiased); this model produces an estimate of 47.1%.
I’ve left out the Lonergan mobile-only poll with n < 900; given that it was mobile-only, robo, I would have entered it into the model with its own unknown house effect. A pollster with an unknown house effect sees the impact of their estimate be greatly diminished, since the uncertainty generated by not knowing their house effect (and having only one poll with which to estimate it) winds up dramatically downweighting the effect of the poll on the overall estimate. Since this was a poll with a reasonably small sample size, it would have had a very small impact on the results in any event. I'll go ahead and re-run the models now with it in, but it won't change much at all, I should think.
Morgan multi-mode at 46.5 is interesting. Morgan multi-mode was showing a house effect of ALP +2, but then the last poll comes in very very close to the model consensus, dragging down the model consensus (even with some discount terms in the model) a little. There'll be time for "drop one pollster at a time" sensitivity analyses after the election, etc.
Update (7.38am AEST): it turns out that Morgan’s final numbers differed slightly from those I had in the analysis, same TPP estimate, just bigger stated sample size and the field period closed Sept 6. Re-running…
Update (10.31am AEST): No change. Lonergan and fixed Morgan field period and sample size leave model estimate at 46.2% ALP TPP. See the graph above.