Thursday, 26 June 2003

Less than Least?

Joy passes along word that the ACC plan is now to just take Miami and, in a bizarre reversal, just Virginia Tech, to create an eleven-team conference. Presumably they’re still looking for a twelfth so they can have a championship game, although maybe they’re just hoping that some of that “11-team cachet” will accrue to them from the Grande Onze (a.k.a. Big Ten), which seems most unlikely. (It’s also a possiblity that the Virginia Tech offer is being made for show, so Virginia’s A.D. can save face with the local politicos, but with no expectation that Tech will accept it.)

If they’re still looking for a #12, my guess is that the contenders are: Central Florida, South Carolina (highly unlikely to leave the SEC), Southern Florida, and East Carolina—schools that fit geographically with either legit second-tier football credibility (as is the case for all but USF) or a good shot at credibility due to recruiting ties in talent-rich Florida (UCF and USF—not every high school standout can go to one of the Big Three). With Virginia Tech in the mix, they don’t have to worry about getting anyone else at the top tier, so a later invite for B.C. or Syracuse seems highly unlikely.

Meanwhile, losing both VT and Miami would effectively strip the rump Big East of what few shreds of BCS credibility it would have had with Tech still on-board; they’ll be lucky if they get to keep the guaranteed slot long enough to lure anyone else into the conference with it—and, in any event, the only top-tier team that the rump Big East could attract is Notre Dame, and it doesn’t need the slot (having made its own sweetheart deal with the four BCS bowls). While the Big East may survive in some form, Big East football will almost certainly be history.

Item-response theory and public opinion

One of the things I’m wrestling with in my dissertation is how best to measure political sophistication or political expertise: roughly speaking, the degree to which a citizen is capable of making informed voting decisions. To do that, I’ve been using (in some places) an item-response theory model, borrowed from the psychometric and educational testing literature. These models assume that there’s a latent trait (or “ability“) that we can’t directly observe, but we can get at that ability by looking at how people answer a bunch of questions. Political expertise is a fairly straightforward application of this approach, but others have applied it to other political problems, most notably the “ideal-point estimation” problem (the most famous example of this is Keith Poole and Howard Rosenthal’s work on Congress using NOMINATE, but Simon Jackman and others have been doing important work in this area too), and the much of the field of structural equation models (or LISREL models) works on generalized versions of this problem.

What does this have to do with public opinion, per se? Well, I was thinking about the abortion issue, where each side wants to coopt as many “reasonable” people into its coalition as possible. The pro-life crowd uses slogans like “choose life” (surely nobody would “choose death,” as a recent correspondent suggested) while the pro-choice crowd tries to promote itself as “supporting family planning” (again, who would oppose that?).

Now, let’s transform this into a public opinion example. If we ask people whether or not they agree with just one of these statements, we’ll get very uninformative results; a few “die-hard” pro-choicers will recognize “choose life” as a pro-life codephrase and disagree, while a few “hardcore” pro-lifers would see “family planning” as a euphemism for abortion rights and oppose that. But most people (including myself) would agree with either statement, which would make them appear to be simultaneously “pro-choice” and “pro-life.” Is the public really this schizophrenic? Probably not; the question wording creates bias (systematic error).

Now, assume we solicit agreement or disagreement with both statements. That gives us two data points, which reflect—to some degree—the underlying attitude of the voter on abortion rights (our “latent trait” of interest). Every additional question (so long as it’s reflecting the same attitude!) gives us more leverage on the latent trait; we might, for example, ask voters whether or not they agree with abortion under particular sets of circumstances (e.g. if the mother’s life is in danger; if the child will have a birth defect; if the conception was due to rape; if the conception was incestuous; if the conception was due to the failure of other birth control; if the parent is a minor; etc.). But even using those two, very biased, questions together will give us a much better picture of the latent attitude toward abortion than just taking one of them alone. And even if the questions aren’t that biased, multiple questions beat a single question any day.

So, the moral of the story is: don’t rely on the marginals from a single survey question unless you just can’t possibly avoid it. And by “can’t possibly avoid it,” I mean “you’re stuck using data collected by people who didn’t (or couldn’t, if it was done before the 1970s) read Converse.”

If this part of public opinion is of interest to you, I strongly recommend reading The Nature and Origins of Mass Opinion, which is probably the definitive modern work in the field.