The Greater New Orleans Community Data Center says the city's population is about seventy-seven percent of what it was before Katrina.

VOA: special.2010.01.22

But you can imagine the inability to do that in a big population study with thousands and thousands of subjects, so we have to rely on data like this.

但你们可以想象在一个大样本研究中,不可能对数以千计的研究对象做这种培训,所以我们需要依靠像这样的数据

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选