A Best Seller as 4 Films Tied Together With Talk

New York Times movie review "A Best Seller as 4 Films Tied Together With Talk" (September 30th, 2010) concerning the Freakonomics movie is in error in its report on an experiment in public high schools run by John List and Steven Levitt. It gets the payment method wrong in multiple ways.

The Grady-Ewing vignette, filmed in a vérité style, follows an experiment in which ninth graders at a Chicago high school were paid to improve their grades: $50 for every grade above a C and the chance to win a $500 lottery.

To qualify for payment, all students had to have all grades be C or higher, no in-school or out-of-school suspensions, and no more than one unexcused absence. If they qualified, 50% would be paid $50. The other 50% would be given a 10% chance at $500. Further, for 50% of either group, the parents would be paid. For the other, the students would be paid. (That is, there were four treatment groups and a control).

The Times gets the threshold wrong, eschews the payment of parents, and gets the payment doubly wrong.