Do gun laws save lives?

Somebody pointed me at this interesting data the other day. The chart above (click to zoom) combines the “Gun Law Score Card” from the Law Center to Prevent Gun Violence in the US with homicide rate data from Wikipedia and voting results from the last US election. Do gun laws reduce the chance of being murdered?

Obviously, “Blue” states tend to have stricter gun laws than “Red” states (an average of B− vs D−). “Blue” states also have lower homicide rates than “Red” states (4.5 vs 5.9), and this is statistically significant (p = 0.012). There is a weak (R2 = 6%) correlation between gun laws and homicide rates, but this relationship is not statistically significant.

Whatever it is that makes you less likely to be murdered in some states than others, it does not primarily seem to be the gun laws. Poverty may be one of the relevant factors, however – median household income explains 22% of the variance in homicide rates, and when this is taken into account, any effects due to gun laws or election results disappear. “Red” states are, on the whole, simply poorer (and, conversely, poor states are more likely to vote Republican and have weak gun laws). Other demographic factors, such as the number of people with college degrees, also seem to have explanatory value as far as the murder rate is concerned. However, the phenomenon of murder does not seem to be understood as well as it could be.


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Logic in a box!

Having recently spent some time teaching a short course on logic and critical thinking, here is the core of the course reduced down to a box of 54 cards. These include:

  • 15 logic cards (summarising basic syllogistic and propositional logic rules),
  • 19 cards illustrating logical fallacies,
  • 5 cards for testing your ability to check validity, and
  • 15 logic-puzzle cards.

If you’re interested, more details can be downloaded from the game page (see the links in the “Downloads” section). The picture below shows some of the cards:


The moons of Saturn

In honour of the Cassini probe, the diagram above shows (to scale) the larger moons of Saturn (those over 100 km in diameter). The moons are shown in order of distance from Saturn, with Janus and Epimetheus being the closest. Titan comes between Rhea and Hyperion.

Janus, Epimetheus, Mimas, Rhea, and Phoebe are shown in black-and-white. Enceladus, Tethys, and Dione are shown in enhanced colour (combining infrared, visible, and ultraviolet). Titan is shown in infrared, which penetrates the atmospheric haze. Hyperion is in true colour, and Iapetus in false colour. Click on the image to zoom.


Origins of the alphabet

This chart shows the origins of the Phoenician, Hebrew, Greek, and Latin alphabets. The Phoenician alphabet is adapted from Egyptian hieroglyphs, but the exact pictorial origins are rather uncertain. The specific Phoenician alphabet used is from here. The chart was produced using R.


On having multiple hypotheses which all fit the data

For every fact there is an infinity of hypotheses.” – from Robert Pirsig, Zen and the Art of Motorcycle Maintenance


‘I will read the inventory… First item: A very considerable hoard of precious stones, nearly all diamonds, and all of them loose, without any setting whatever… Second item: Heaps and heaps of loose snuff, not kept in a horn, or even a pouch, but lying in heaps… Third item: Here and there about the house curious little heaps of minute pieces of metal, some like steel springs and some in the form of microscopic wheels… Fourth item: The wax candles, which have to be stuck in bottle necks because there is nothing else to stick them in… By no stretch of fancy can the human mind connect together snuff and diamonds and wax and loose clockwork.’

‘I think I see the connection,’ said the priest. ‘This Glengyle was mad against the French Revolution. He was an enthusiast for the ancien regime, and was trying to re-enact literally the family life of the last Bourbons. He had snuff because it was the eighteenth century luxury; wax candles, because they were the eighteenth century lighting; the mechanical bits of iron represent the locksmith hobby of Louis XVI; the diamonds are for the Diamond Necklace of Marie Antoinette.’

Both the other men were staring at him with round eyes. ‘What a perfectly extraordinary notion!” cried Flambeau. “Do you really think that is the truth?’

‘I am perfectly sure it isn’t,’ answered Father Brown, ‘only you said that nobody could connect snuff and diamonds and clockwork and candles. I give you that connection off-hand. The real truth, I am very sure, lies deeper.’

He paused a moment and listened to the wailing of the wind in the turrets. Then he said, ‘The late Earl of Glengyle was a thief. He lived a second and darker life as a desperate housebreaker. He did not have any candlesticks because he only used these candles cut short in the little lantern he carried. The snuff he employed as the fiercest French criminals have used pepper: to fling it suddenly in dense masses in the face of a captor or pursuer. But the final proof is in the curious coincidence of the diamonds and the small steel wheels. Surely that makes everything plain to you? Diamonds and small steel wheels are the only two instruments with which you can cut out a pane of glass.’

The bough of a broken pine tree lashed heavily in the blast against the windowpane behind them, as if in parody of a burglar, but they did not turn round. Their eyes were fastened on Father Brown. ‘Diamonds and small wheels,’ repeated Craven ruminating. ‘Is that all that makes you think it the true explanation?’

‘I don’t think it the true explanation,’ replied the priest placidly; ‘but you said that nobody could connect the four things. The true tale, of course, is something much more humdrum. Glengyle had found, or thought he had found, precious stones on his estate. Somebody had bamboozled him with those loose brilliants, saying they were found in the castle caverns. The little wheels are some diamond-cutting affair. He had to do the thing very roughly and in a small way, with the help of a few shepherds or rude fellows on these hills. Snuff is the one great luxury of such Scotch shepherds; it’s the one thing with which you can bribe them. They didn’t have candlesticks because they didn’t want them; they held the candles in their hands when they explored the caves.’

‘Is that all?’ asked Flambeau after a long pause. ‘Have we got to the dull truth at last?’ ‘Oh, no,’ said Father Brown.

As the wind died in the most distant pine woods with a long hoot as of mockery Father Brown, with an utterly impassive face, went on: ‘I only suggested that because you said one could not plausibly connect snuff with clockwork or candles with bright stones. Ten false philosophies will fit the universe; ten false theories will fit Glengyle Castle. But we want the real explanation of the castle and the universe.” – from G. K. Chesterton, “The Honour of Israel Gow