Roland Fryer and the DC public schools

Fryer leaves a policy evaluation research venture because the DC schools and their associated teacher labor cartel will not do random assignment.

And, what is not unrelated to the fact that very few policies get evaluated in any sort of serious way, the Washington Post columnist (and, by implication, his editor as well) shows that he does not understand the difference between random assignment and random sampling:

What ultimately sank the venture was Fryer’s interest in randomly assigning some teachers into “treatment” and “control” groups. Random assignment is considered one of the strongest research designs because it ensures that the sample selected represents the characteristics of the entire group under study.

Sigh. We do indeed have a great deal of work to do.