Tuesday, January 13, 2015

Standardized tests and your cat’s body mass index

Someone recently showed me this system for measuring a cat’s body mass index. (Don’t ask why.) The system requires you to measure your cat’s girth and lower hindlimb and then plug those measurements into a formula containing numbers that go to the fourth decimal place. Don’t divide by 0.7063; make sure it’s 0.7062.

Four decimal places! Of course, a measurement is only as precise as its least precise input. Call me crazy, but I think I’m a long way from being able to measure my cat’s “lower hindlimb” with enough accuracy to justify using multipliers that go to the fourth decimal place.

I thought of cat BMI when I read the state task force’s report recommending that Iowa adopt the expensive, computer-based Smarter Balanced Assessments:
Computer-adaptive testing, where the computer selects more or less difficult items based on the student’s answers to prior questions, is better able to pinpoint (more reliably and with fewer items than a fixed-form assessment) the performance of students performing at both high and low levels of performance (e.g., students who are gifted, students with disabilities). This means more precise scores for Iowa students.
Better able to pinpoint the performance of students performing at both high and low levels of performance! Now, maybe you’re different from me, and maybe one of your big worries is that the annual standardized tests aren’t pinpointing your child’s performance precisely enough. Even so, do you really believe that any standardized test, no matter how good, could “pinpoint” your child’s academic “performance”?

Schools are constantly reminding us that kids’ test scores can vary depending on how much they’ve slept and what they ate for breakfast. There’s even evidence that scores are affected by random events like variations in air pollution and whether there’s been a recent violent crime near the school. Then there’s the question of whether a student is really trying to do well on the tests, or just trying to get through them—a question that will only grow larger when the tests take twice as many hours. So how precisely can these tests possibly measure your child’s ability?

And never mind that the whole assessment regimen is built on the assumption that the Iowa Core standards are themselves some kind of precision instrument, and that “performance” will be maximized by preventing even small departures from their supreme wisdom. It must be reassuring for education officials to imagine such a well-oiled machine. But there’s no empirical basis for the assumption that the Common Core is precisely the best way to turn your child into a capable adult.

There’s no point in obsessing over precision at the top of the pyramid, when it’s non-precise assumptions from there on down.

The task force would have you believe that standardized tests are like thermometers, and that more money buys you more decimal places in the temperature reading. If you believe that, I’ve got a Feline Fitbit I’d like to sell you.


M.L. said...

Best post EVER!

Chris said...

Thanks, M.L. I couldn't have a series of posts on standardized testing without at least one reference to fat cats.

Yastreblyansky said...

Great post! Glad you sent it to the Roudup.