Sunday, February 1, 2015

Bayesian updates for Galaxy and IPSOS

Over the weekend we have two new polls. Both cast more light on the political impact of awarding a Knight of the Order of Australia to the Prince Consort: IPSOS (46-54; -2 on the first week of December for the Coalition) and Galaxy (43-57; also -2 for the Coalition on the first week of December). Individually, both polls suggest a movement of voting intention away from the government of two percentage points since the first week of December.

However, the Bayesian model was not convinced. In part, given the small number of polls we have from both these houses, it has responded by adjusting the house bias for these houses. But, to be fair, the January 27 ReachTEL poll only had a one point movement away from the government between 20 November and 27 January. Also the December Morgan poll and the latest Morgan poll show a one point movement in favour of the Coalition. Consequently, the Morgan and ReachTEL results would have mediated the latest IPSOS and Galaxy movements in the Bayesian model.

While the Bayesian model might not have moved as shockingly for the government as the two most recent polls, it is still moving in the wrong direction for the government. If an election was held now, it would be a thumping landslide win for Labor.

As a very rough rule-of-thumb, we can use the cube rule to estimate the number of seats Labor would win with 55 per cent of the two party preferred vote. That estimate is 97 seats.


  • 5 February 2015 - added maxima, minima and endpoint statistics to the charts (at the request of Andrew Catsaras). Also added an observation based on the cube rule.


  1. Mark, could you note on your graph the actual final number you've calculated. Cheers, Andrew.