The guest list for the dinner provided a sample. Among those seated in the State Dining Room were the first two Muslims elected to the U.S.Congress Keith Ellison and Andre Carson.

VOA: standard.2009.09.02

Covariance is--we'll call it--now we have two random variables, so cov... I'll just talk about it in a sample term.

协方差是...我们有两个随机变量,x和y的协方差是,从样本的角度来说

耶鲁公开课 - 金融市场课程节选