Oz Politics Blog

This is the fourth Newspoll in two weeks. The national two-party preferred vote share prediction, were an election held last weekend, was 60 per cent for Labor and 40 per cent for the Coalition.

Outside of human error, there are four key interpretations for the 5 percentage point jump between Monday to Thursday, and Friday to Sunday in the last week. I have listed them below from (in my view) the least plausible to the most plausible.

• There was a statistically significant shift in voting intention over the week
• The 60-40 per cent result for Friday to Sunday was a rogue poll
• The 55-45 per cent result for Monday to Thursday was a rogue poll
• The underlying population voting intention for Labor was steady around 57 to 58 per cent, and both the 55 and 60 per cent results were within the error margin of 57 to 58 per cent.

I know my view on the most plausible explanation goes against the general approach to inferential statistics, which would opt for my least plausible explanation. In this case, I cannot see a compelling reason to believe the polls moved 5 points in a matter of days. Let’s just say that I am not a slave to p-values less than 0.05 without a compelling theory of action!

I suspect the best way to interpret the recent volatility in the Newspoll series is to take the moving average, which suggests the underlying support for Labor is around 58 per cent of the national two-party preferred vote share. The Coalition gets around 42 per cent of the national TPP vote share.

I remain of the view that the trend has effectively flat-lined since the beginning of April. This view is supported by my chicken entrails analyzer on the polling data since the first of April, which projects a flat line for Morgan, Newspoll and ACNielsen. Perhaps it is not called April fools day without reason.

The election calculator suggests Labor would win around 121 seats, if it managed to secure 60 per cent of the national two-party preferred vote at an election. It would win 111 seats if it managed to secure its medium term average of 58 per cent.

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