He says the class action failed because it did not target a single action or policy by Wal-Mart.

VOA: special.2011.06.24

It worked out kind of nicely because after that I would have a single class on Thursday

这样的日子能撑过去是因为我周四只有一节课，

耶鲁的忙碌生活 - SpeakingMax英语口语达人

In principle, we could play this with the whole class, but let's single out a particular row of the class so I'm going to come down here and I guess eventually, well I'll grab it in a minute.

理论上,我们可以全班一起做这个博弈,但我要选出特定的一行,我先走下来,我觉得,我很快就能挑到人

耶鲁公开课 - 博弈论课程节选