Tag Archives: statistics

Recognising phoney on-line reviews

Surprise, surprise! The marketing value of positive on-line user-reviews has created an industry of liars-for-hire, ready to pimp any product with phoney “user” endorsements. Hotels, cafs, publishers, music labels and (horror!) even bloggers can readily find cut-price on-line testimonialists to pimp their product on sites like fiverr.com. Unfortunately, there’s a good chance we’ll fail to […]

Temperature trends in Garnaut 2011

I remain unconvinced by Dr Garnaut’s arguments that global average temperature trends in the past decade should, if anything, add to a sense of alarm about man-made “greenhouse-gas” emissions. There is much in the updated review that I have not had an opportunity yet to consider. (Update: There’s a more comprehensive critique of the updated […]

Trade ‘imbalances’ are misleading

Alexandro Jara, the Deputy Director-General of WTO “[R]elying on conventional trade statistics gives a distorted picture of trade imbalances between countries. As we saw when looking at the Chinese content of the iPad, what counts is not the imbalances as measured by gross values of exports and imports, but how much valued added is embedded […]

Offensive teenagers

Offenders By Age And Sex

According to the Australian Bureau of Statistics more than 1 in 12 teenage males commits an offense that comes to police notice.

Rahmstorf rebuffed

The Potsdam Institute physicist whose 2007 paper Ross Garnaut relied on for his assertion that “on the balance of probabilities” CO2-driven warming was accelerating dangerously, has been exposed as a scientific gadfly.

At the time of the publication of Garnaut’s interim report, several well-qualified sceptics disputed Rahmstorf’s projetions, including David Stockwell, Lucia Liljegren and Steve McIntyre with strong support from former Australian statistician Ian Castles. Ian also kindly supported my request to the Statistical Society of Australia to evaluate the Rahmstorf methodology in the interests of better informed public debate on Garnaut’s recommendations (they eventually declined).

Now, A UK Met Office researcher and oceanographers have harshly criticised Stefan Rahmstorf for his extravagant prediction that warming would lead to sea-level rises of 1.88 meters by the end of the century.

“Critic Simon Holgate, a sea-level expert at the Proudman Oceanographic Laboratory, Merseyside, has written to Science magazine, attacking Professor Rahmstorf’s work as ‘simplistic’.

‘Rahmstorf’s real skill seems to be in publishing extreme papers just before big conferences like Copenhagen, when they are guaranteed attention,’ Dr Holgate said.” Extract from Sea-level theory cuts no ice | The Australian

Interesting to note Rahmstorf’s weasly response to the criticism, reported at the end of The Australian’s story.

The ABS explains “trend estimates”

I’ve argued several times that the broadcast media has misrepresented quarterly unemployment by focusing on (the scarier of either) the raw or seasonally-adjusted data. Although there’s a great deal to be said for just eyballing a trend when you have a long time-series that accurately samples an ‘atomic’ phenomenon, trends in a series with statistically simple (‘normally distributed’) variability, like unemployment, can reasonably be represented by a smoothed trend estimate.

“Trend estimates are obtained by smoothing the seasonally adjusted estimates, with an assumption that the irregular component is random and normally distributed. Distortion of the trend estimate will occur in the presence of an unusual event, and if no correction for the impact is introduced, then the trend estimate can be misleading.” Extract from 1350.0 – Australian Economic Indicators, Aug 2009

As the ABS release argues, this procedure goes wrong when it’s no longer ‘business as usual.’ But the assumption that the world today is just like the world yesterday is both prudent and pretty successful, especially at the leading edge of a trend with established variation. Correlation of smoothed data series is a different matter: it may be a species of fraud.

U.S. and Global Temperatures: a correction

Corrected GISS record shows 1934 as the hottest year

Dr Gavin Schmidt, a climate modeler at NASA and a principal author of the Real Climate weblog, has emailed me to point out an error (mine) in my review of Ian Plimer’s Heaven + Earth.

I said that I had learned from Ian Plimer that NASA had reversed it’s claim that the ten years following 1995 were the hottest ten years of the century when Steven McIntyre showed that the record belonged to 1934. But, as Dr Schmidt points out, 1934 was the hottest year in the GISS records only for the United States, not in the global GISS records. He goes on to accuse Prof. Plimer of ‘lying’ to his readers about this, and other, matters.

I am grateful to Dr Schmidt for pointing out this error, which I have corrected. But I still share Ian Plimer’s amply-documented conclusion that there is no reason for alarm about the slight warming that undoubtedly took place over a fifty year period from the 1940s.