empirical cdf的最大值也隻能是1,所以variance還是0。你給的link是說empirical cdf的variance。Wiki也有定義,http://en.wikipedia.org/wiki/Empirical_distribution_function#Definition
看看這個對你有用嗎:https://www.scss.tcd.ie/Rozenn.Dahyot/ST2002/20080130IntroductionSE.pdf
這裏說的那個Dirac delta function,就不是我能理解的了。就如wiki說的,“From a purely mathematical viewpoint, the Dirac delta is not strictly a function, because any extended-real function that is equal to zero everywhere but a single point must have total integral zero。”, 可是這個function的integral = 1。估計measure theory好的人才能看明白你的問題了。