Free Thought

In this column, Richard Muller claims that McKitrick and McIntyre have shown that the hockey stick graph is an "artifact of poor mathematics". If you have been following the global warming debate this claim should look familiar, because McKitrick and McIntyre made the same claim last year as well. So what's new? Well, last year they claimed that the hockey stick was the product "collation errors, unjustifiable truncations of extrapolation of source data, obsolete data, geographical location errors, incorrect calculations of principal…
The graph above, which Iain Murray claimed showed that "The fact that the ten hottest years happened since 1991 may well be an artifact of the collapse in the number of weather monitoring stations contributing to the global temperature calculations following the fall of communism (see graph)" comes from this paper by Ross McKitrick. McKitrick recently was in the news for publishing a controversial paper that claimed that an "audit" of the commonly accepted reconstruction of temperatures over the past 1000 years was incorrect, so I thought it would be…
R2 values using county-level 1977-2000 (Corresponds to Lott's corrected Table 3a)   Violent Crime Murder Rape Aggrvtd Assault Rbbry Prprty Crimes Auto Theft Brglry Lrcny R2 without any shall-issue variable 0.86 0.81 0.76 0.80 0.91 0.81 0.84 0.81 0.80 R2 (Single dummy variable model) 0.86 0.81 0.76 0.80 0.91 0.82 0.85 0.81 0.80 R2 (Spline model) 0.86 0.81 0.76 0.81 0.91 0.82 0.85 0.81 0.80 R2 (Hybrid model) 0.86 0.81 0.76 0.81 0.91 0.82 0.85 0.81 0.80 Values that have increased when the shall-issue variable is added are in bold. My thanks to David Powell for computing these values.
Crime rates go up and crime rates go down. Before seizing on some possibly coincidental factor such as gun training or gun control as the cause of the change, we need to establish if the change was unusual, i.e. statistically significant. The only attempt I have seen to establish this is in Kleck and Bordua's paper which claims that the change was significant since it exceeded two standard deviations. This is wrong. A rate two standard deviations from the mean would be significant, but changes exceeding two standard deviations occur 15% of the time for normal variates, nowhere near the 5%…
If you want to consider population density, Alaska has a density 7 times that of Yukon. This is a rather enormous difference. Andy Freeman said: But, is it a significant one? The relative size of the empty spaces probably doesn't matter much, except when it comes to computing average population density, because we really can ignore places where there's no one around to kill or be killed. I think it is up to those who claim that the two places are comparable, to show that, ignoring uninhabited areas, the densities are the same. Here is another way they differ: % of population living in…
The Terminator said: Excluding the United States and Switzerland would make this worse. Further, do you have any justification for excluding them? Eliminating data points, simply because they don't "fit" isn't very good methodology. Because with least squares estimation, outlying values bias the results. In this case they make the correlation higher, giving a value that would be quoted by a politician, and not a statistician. I made the same mistake on an oral presentation a semester ago. I was computing a linear regression for data taken in the Millikan Oil Drop Experiment. I "threw out"…