Le Bron and Grades

March 21, 2018
Posted by Jay Livingston

I’ve never used those percentages in grading – you know, 94% is an A, 82% is a B– and so on. Eighty-two percent of what, I wonder, especially on essays? The percent may be just the same subjective judgment of an essay, but one that makes it seem more precise and objective. You can’t argue with numbers. 

I do use points – a point for each multiple-choice or short answer, so many points for a short essay, more for a long essay – to weight different parts of the exam. But I don’t use a standard formula for converting exam scores to letter grades. Instead, I adjust my own idea of what the grades should be to the actual distribution of scores in the class.

I explain this on the first day of class, and I post a document (“How I Grade”) on Canvas at the start of the semester, but apparently neither of those is very convincing. Students see their scores on Canvas, which also converts these to percents. The student who sees 55% on Canvas comes to class convinced it’s a failure. Even when I give them my own number-to-letters conversion for the exam, some remain skeptical. It’s as though I were singing my own made-up lyrics to some well-known song. They hear, but deep down they know, “Those aren’t the real words.”
I came up with a new strategy this week when I gave back the midterms. “Who’s the best basketball player in the NBA?” I asked. Everyone knew: LeBron James.

“What’s LeBron’s field-goal percentage?” The few students who had some idea lowballed it, guessing 40-45%. “Actually, he’s having a good year,” I said. “He’s hitting about 55%.” Then. “So I guess that means LeBron gets an F in basketball.”

That analogy may have done the trick – that, plus a letter grade that was higher than what they had expected.

Drugs and Death Penalties

March 13, 2018
Posted by Jay Livingston

It’s a sure sign of desperation when a politician calls for the death penalty for drug dealing.

Trump is basically admitting that his administration has no idea how to solve the drug problem.

Two hundred fifty years ago, Cesare Beccaria argued that of the three elements of punishment – certainty, swiftness, and severity – severity is the least effective. All the subsequent research has proven him right. But certainty and swiftness are hard to increase; severity is easy. Just pass some laws imposing long sentences, mandatory sentences, life sentences, and of course, death. When politicians call for the death penalty what they are saying is, “We don’t know how to catch very many of these guys, and it takes a long while before they are actually sentenced, so when we do catch one of them, we’re going to show him how pissed off we are.”

Draconian punishments may be very good for expressing the frustration and anger of law-abiding people, and Trump is very good at playing to those emotions. But as for the practical effects, executions are unlikely to have much of an impact on crime. What was true in in the crack crisis of the 1980s is still true: there already is in fact a death penalty for drug dealers. It’s just not administered by the state. It’s administered by rival drug dealers. And compared with any death penalty the state might impose, it is carried out with far greater frequency and swiftness.

President Reagan was fond of saying that in the sixties we fought a war on poverty, and poverty won. He was factually wrong. But if he had made the statement about the war on drugs that the government waged in the following decades, he’d have been closer to the truth. Those years when drugs were winning the war also gave us the spectacle of politicians falling all over themselves to pass harsher and harsher drug laws. Conservative politicians them sounded very much like Trump today. And like Trump today, many of them, perhaps, thought that in this way they were “doing something” about drugs. Of course, what they were more certain of was that they were doing something about getting re-elected.

Ass-Backwards Through the Gateway

March 11, 2018
Posted by Jay Livingston

Imagine that you’re a US Attorney on the drug beat. Your boss is Jeff Sessions, who has announced that he’s going to vigorously enforce laws against marijuana and use the federal law when state laws are more lax. Maybe you also think that weed is a dangerous drug. You do a little “research” and tweet out your findings.

This brief tweet might serve as an example of how not to do real research. The sample, which excludes people who have not gone to treatment centers, is hardly representative of all users. There’s researcher bias since the guy with the ax to grind is the one asking the questions. The respondents too (the drug counselors) no doubt feel some pressure to give the Sessions-politically-correct answer. They may also be selectively remembering their patients. 

But even without the obvious bias, this tweet makes an error that mars research on less contentious issues. It samples on the dependent variable. The use of heavier drugs (opioids, heroin, meth, etc.) is the dependent variable – the outcome you are trying to predict. Marijuana use is the independent variable – the one you use to make that prediction. Taking your sample from confirmed heroin/opioid addicts gets things backwards. To see if weed makes a difference, you have to compare weed users with those who do not use and then see how many in each group take up more serious drugs.

Here’s an analogy – back pain. Suppose that, thanks to advances in imaging (MRIs and the like) doctors find that many of the people who show up with back pain have spinal abnormalities, especially disk bulges and protrusions. These bugles must be the gateway to back pain. So the doctors start doing more surgeries to correct these bulges. These surgeries often fail to improve things.

The doctors were sampling on the dependent variable (back pain), not on the independent variable (disk bulges). The right way to find out if spinal abnormalities cause back pain is to take MRIs of all people, not just those who show up in the doctor’s office. Eventually, researchers started doing this and found that lots of people with spinal abnormalities did not pass through the gateway and on to back pain.

The same problem often plagues explanations that try to reverse-engineer success. Find a bunch of highly effective people, then see what habits they share. Or look at some highly successful people (The Beatles, Bill Gates) and discover that early on in their careers they spent 10,000 hours working on their trade.

US Atty. Stuart’s tweet has all the advantages of anecdotal evidence and eyewitness testimony. It’s a good story, and it’s persuasive. But like anecdotal evidence and eyewitness testimony, it is frequently misleading or wrong. The systematic research – many studies over many years – shows little or no gateway effect of marijuana. No wonder US Attorney Stuart chose to ignore that research.*

* As Mark Kleiman has argued, even when a marijuana user does add harder drugs to his repertoire, the causes may have less to do with the drug itself than with the marketplace. The dealer you go to for your weed probably also carries heavier drugs and would be only too happy to sell them to you.  Legalizing weed so that it’s sold openly by specialty shops rather than by criminals may break that link to other drugs.

This Is Not a Pipe . . .

March 7, 2018
Posted by Jay Livingston

. . .  But what is it? Is there a word a statement that contradicts the assertion in the statement?  For example, one of Trump’s better lines at the Gridiron Club was this.

"My staff was concerned that I couldn't do self-deprecating humor, and I told them not to worry, nobody does self deprecating humor better than me. It’s not even close.

Not a new joke, but a good one, especially for Trump.

Self-contradiction does not really convey the delightful irony. Trump contradicts himself all the time but the contradiction is not inherent in the statement itself.

It’s kinda sorta like apophasis (my favorite rhetorical term), but it’s different. I posted about it last summer (here) with Magritte’s painting and this unwitting example that was going around the Internet.

I still haven’t found le mot juste for it.