Tuesday, February 5, 2013

Weekly poll aggregation

This week we have two and a half new opinion polls. One of them - Newspoll - lurched dramatically to the Coalition. Three weeks ago, the Newspoll two-party-preferred estimate was 51 to 49 in the Coalition's favour. Last weekend, the Newspoll estimate was 56 to 44 in the Coalition's favour. A five percentage point movement.

Last weekend's Galaxy poll was pretty much unchanged from the beginning of December (which is consistent with the aggregated poll as it was until last week). For the rolling fortnightly poll from Essential (half of which was sampled last weekend and the other half during the previous weekend) we also have a steady-as-she-goes poll result. All of which leaves me wondering, is the Newspoll result a rogue poll?

While "rogue" (at least in part) would be my hunch, there is currently no way of knowing for sure. We will need to see a few more polls before we can form an informed judgement on this particular poll. Nonetheless, such a dramatic movement in this Newspoll has moved the aggregated poll result (albeit less so).

Update 6 February

Morgan has broken with its usual practice and released a weekly poll: 50.5 to 49.5 in the Coalition's favour. This was a one-percentage point move to the Coalition over the previous fortnightly poll. Dropping these numbers into the Bayesian model sees an unchanged endpoint:

Update 8 February

I have been asked about the latest LOESS aggregation. At 47.1 per cent, it yields a very similar result to the Bayesian aggregation.

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