July 8, 2004

Net-flow SAS test files

After talking with my colleague John Ferron, I've tried to use the SAS DATA step to calculate the net-flow rates and then to vary the retention-rate estimates randomly around the official figures, to see how that changes the results.

I'm not surprised that the most fragile estimates are net flows at 8th and 9th grades, because retention rates are typically highest in 9th grade and it's in 8th and 9th grades when students start to drop out of school in larger numbers. The retention rate affects the net-flow estimates most for that grade and the grade below it. (The algebraic expressions for the estimates only include data from the grades surrounding the grade in question, but the iterative process creates a larger influence down the grades from a specific retention rate. Regression on the Monte Carlo data sets strongly suggests that the influence is highest on the grade below, then on the same grade, and then the retention rate's influence on net-flow estimates sharply decreases for other grades.)

The most surprising feature for the Florida 2000-01 case is the estimated net in-flow during 8th grade. I suspect that's an artifact of the data to some extent—an underestimate in 9th grade retention would boost the implied net in-flow for 8th and increase the implied net out-flow for 9th. But the official retention rate for 9th graders in Florida for 2000-01 is 25% (calculated from end-of-year rolls to the beginning of the next year). Could it be higher? The other moderate influence could be the distance between promotion time and enrollment-counting time. I've been assuming that Florida's August start time is about 85% of the way through an October-to-October enrollment-counting cycle (which is what the federal government wants for its Common Core of Data, my source for enrollment). But if the enrollment is a beginning-of-year count, the figures are a little less anomalous.

The files

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Posted in Research on July 8, 2004 7:15 AM |