16 August 2016

Misusing science to further an agenda risks harming both

Anyone who has anything to do with science will have had a conversation with someone whose attitude can be summarised as, "Huh. Scientists. What do they know? Last year they said eating butter/smoking cigarettes/injecting heroin/playing frisbee with a lump of plutonium was bad for us, now they say it's good."

Several years ago, I would tell such people that it wasn't the scientists who were the problem; rather, it was the journalists who were distorting things to get a cool story.  Then I got a bit closer to science, and I started to ask myself some questions.  It seemed like, in many cases, the scientists were not entirely innocent.  It turned out that researchers themselves, or their institutions' press departments, will often spin a piece of research into a cute story; in some cases, I suspect that the press release is written even before the first participant is recruited.

But this particular story takes me back to the old days.  Terrible reporting of an innocent study, just to fill column inches (or, more likely these days, to provoke clicks).

The study in question is Market Signals: Evidence on the Determinants and Consequences of School Choice from a Citywide Lottery, by Steven Glazerman and Dallas Dotter.  (You can download the full article as a PDF file from the page I linked to.)  The authors examined the behaviour of parents whose children were about to enter, or change school within, the school system of Washington, DC.  Basically, not everybody can get to go to their first choice of school, so parents rank a selection of schools in descending order of preference, and then a computer tries to assign as many people as possible to a choice that is as high on their list as possible.

Parents didn't give reasons for their choice of rank ordering, but Glazerman and Dotter reasoned that it might be possible to examine their choices and see what factors were influencing them.  For example, it seems reasonable that the further a school is from your home, the less likely you are going to be to want to send your child there, all other things being equal.  On the other hand, if there's a good bus service, that might offset the distance factor, perhaps especially for older kids who can ride the bus on their own.

These kinds of studies can often provide useful information for people who are planning educational and other resources.  Indeed, Glazerman and Dotter were interested in seeing what factors actually drive parental preference for schools, as a way to help school systems plan where to put their schools, how large to make them, etc.  For example, if they were to discover that distance actually has a very small effect if there is a good bus service, that might allow planners to feel better about moving a school to a greenfield site some way removed from where people live, and provide extra buses, rather than trying to expand the school in a limited space in its current location.  It's all very wonkish, numerical stuff --- indeed, the article comes from an organisation called "Mathematica Policy Research".

Now, one of the factors that Glazerman and Dotter examined was ethnicity (or race, or whatever you want to call it).  In the study, parents and their children were categorised as "White", "African American", or "Hispanic".  (For the purposes of this post, I'll ignore awkward questions about mixed-race families, or indeed the meaning of race and ethnicity; this post isn't really about that, although of course as a white person I have my own baggage here.)  Also, data were available on the ethnic mix of the children already attending each school.  So one of the factors that the authors were able to tease out from their data was the extent to which the proportion of students of ethnicity X in a school affected the preference of parents of ethnicity X for that school.

I've taken the liberty of reproducing Table 7 from the article here (apologies to people reading this on a mobile device).  To see how the model works, look at the first section, "Convenience", and the first line within that, "Distance (miles)".  For each of three school age ranges, and for each of three ethnicities, there is a number showing the effect of distance from home to school on parents' likelihood of choosing any given school.  All of the numbers are negative, which means that the model appears to be working: A greater distance has a negative effect on your willingness to choose that school.  And as a bonus, this effect is larger for elementary school, which makes sense (to me, anyway) --- it's more important that your smaller kids' elementary school is closer to your home than their big siblings' high school.  (The actual numbers in the table are standardised, so they don't have any meaning outside the table; just remember that bigger numbers mean a stronger positive or negative preference.)

Now look at the section entitled "School Demographics".  It gets a little complicated here because the authors found that a quadratic relation between demographics and likelihood of choosing provided a slightly better fit to the data, but basically, the same rules hold: A positive number means a preference for the same ethnicity, and a larger number means a stronger preference.  The quadratic terms are not very large, so for the purposes of this post, we can look at just the first line in this section, "Own-race percentage/10". In contrast to home-to-school distance, the results for ethnicity are not very consistent.  For White parents, there is a coefficient of 0.109 (i.e., an apparent preference) for a larger number of White students in their kids' elementary school, and the stars next to this value mean that it is statistically significant, suggesting that there was little variability among parents on this measure.  On the other hand, African American parents have a statistically significant coefficient of 0.188 for their preference for seeing more students of the same ethnicity in middle school, and for Hispanic parents, the coefficient for their preference for more Hispanic kids in high school is even higher at 0.485.

These numbers don't immediately seem to make a lot of sense to me.  Maybe there are some other factor driving them.  Remember, parents didn't explicitly state "I want my kid to go to a school with lots of people who look like him/her"; this was inferred from their expressed preferences of school, and the ethnic makeup of that school.  It might be that there are other factors driving these choices that the authors didn't (or couldn't) measure, or it could be that there is a lot of noise in their model.  The article is only a "Working Paper", meaning it hasn't been published in a peer-reviewed academic journal yet.

However, here's how this was written up in Slate by Dana Goldstein: "One Reason School Segregation Persists: White parents want it that way."  I encourage you to read that piece after first reading Glazerman and Dotter's carefully-written study.  The Slate article is a collection of cherry-picked items designed to support an agenda.  Here's the cherry-picking in full:
Across race and class, a middle-school parent was 12 percent more likely to choose a school where his child’s race made up 20 percent of the study body, compared with a school with similar test scores where his child’s race made up only 10 percent of the study body. White and higher-income applicants had the strongest preferences for their children to remain in-group, while black elementary school parents were essentially “indifferent” to a school’s racial makeup, the researchers found. The findings for Hispanic elementary and middle school parents were not statistically significant.
Let's unpack that.  The first statement doesn't tell us anything about ethnic bias, other than the rather unsurprising news that parents of all races would apparently slightly prefer their kids to be in a 20% minority versus a 10% minority.  (After all, Everyone's a Little Bit Racist.) The second sentence is a masterpiece of careful drafting.  First, note "White and higher-income applicants".  Everyone knows that White people tend to have higher incomes, so this is just rhetorical double-dipping, hiding the fact that higher-income African American and Hispanic parents also had a preference for their child to "remain in-group".  That might tell us something about well-off people (perhaps a follow-up article is in the works, telling us about the evils of rich, as opposed to White, people), but it's utterly irrelevant to the claims that this phenomenon is being driven by White people's prejudices.  Second, did you spot that "black elementary school parents were essentially 'indifferent' to a school’s racial makeup"?  That's indeed what the data show.  But Goldstein chose not to tell us that African American parents were apparently very concerned about the racial makeup of middle schools.  And finally, look at the last sentence.  It's also true, but it omits the fact that the coefficient of ethnic preference for Hispanic parents of high school students was statistically significant (and large).  But the net result is clear: The scene is set for the author to tear into the barely-unconscious sins of (only) White parents.

Perspective is everything.  Back in the Cold War, there was a joke that went like this:  The American ambassador to the United Nations challenged the Soviet ambassador to a running race.  The New York Times reported the result: "U.S. ambassador beats Soviet ambassador". Pravda reported: "Soviet ambassador finishes heroic second in race; U.S. ambassador next to last". 

So, let's get some perspective here.  These parents are residents of Washington DC, a city that is 48% Black and 44% White; probably one of the most ethnically mixed cities in the United States, I'm guessing.  It's surrounded by the leafy suburbs of Maryland and northern Virginia, which, from what I've seen on tourist visits to those areas, is where a lot of White people who commute to work in DC tend to live; and they were not part of Glazerman and Dotter's study, which covered District of Columbia residents only.  Those White people who have not become part of the "white flight" to the suburbs are, I suggest, likely to be pretty tolerant of people from other ethnicities.  Indeed, Glazerman and Dotter's results suggest that the percentage of White students at which the attractiveness of ethnic similarity for a middle school peaked was just 26% (i.e., less White than the city as a whole).  This does not suggest some kind of supremacist attitude towards the fellow students of these parents' 11-14 year old children.  (My bet, for what it's worth, is that noise is the best explanation of a lot of these findings, but I'm not here to critique Glazerman and Dotter's study, which I found interesting and informative.)

This could get political, and I don't want it to.  Racism is a bad thing, and mixing ethnicities in schools seems to me to be a good idea.  But journalists with an agenda to find bad things happening ought not to cherry-pick scientific reports in which those bad things have not, in fact, been discovered.  It provides ammunition for the kind of people who use words like "libtard" on social media, and it does a disservice to those who are very likely not part of the problem.  There are any number of other sources of racial disharmony that it would be much more productive to investigate.

I asked Steve Glazerman, one of the authors of the study, for a comment on this.  He replied: "Misinterpretation is an occupational hazard that we occasionally face as researchers”.  Science, especially social science, has plenty of problems right now.  In its efforts to get away from confirmation bias, it doesn't need lazy journalism, demonstrating exactly the same bias, to create false narratives with potentially damaging consequence for public policy.

Dana Goldstein concluded her article with "Because research—and history—show that left to their own devices, parents won’t desegregate schools."  I can't comment on the "history" part of that, although I suspect that it's true, albeit complicated.  But this research says no such thing.  Falsely adopting the legitimacy conferred by "SCIENCE" is dangerous, no matter how well-meant one's agenda might be.

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