Roosevelt Elementary started Year 1 of Elevate with 100 students. It ended the year with 400. The other two schools held roughly steady. The district grew from 600 students to 900, and the composition of that denominator shifted decisively toward the lowest-scoring school. That one fact explains the entire dashboard. Elevate worked. Every school’s average … Read more
Last week’s post ended with a theorem. This one starts with a dashboard. The theorem — Arrow’s impossibility result, applied to the aggregation problem that Simpson’s paradox creates — is on the record in All Measurements Are Local if you want it. The short version: when subgroup results conflict with each other and with the … Read more
A new recurring feature, starting this week. A few items from the news — sometimes updates to arguments this blog has already made, sometimes new events the existing framework illuminates without quite rising to a full post — followed by a couple of things we’re watching that haven’t ripened yet. Everything here is shorter than … Read more
Yesterday’s post argued that a national aggregate can accurately represent no one’s actual experience when the underlying data are structured the right way — or, more precisely, the wrong way. The incarceration example was instructive precisely because it was symmetrically uncomfortable: the same Simpson’s paradox that embarrasses the reform-is-working narrative also embarrasses the cities-are-dangerous one. … Read more
A friend and colleague gave a talk today about incarceration trends in the United States (she knows who she is, and I owe her a coffee). The importance of the problem — and the genuine messiness of the data — got me thinking about how difficult it is to convey the right lessons from debates … Read more