作者skate411 ()
看板Statistics
标题[问题] 机率问题 急
时间Wed Nov 7 21:56:54 2007
An urn contains 2n balls , of which r are red. The balls are randomly removed
in n successive pairs. Let X denote the number of pairs in which both balls
are red.
a).E[X]
b).Var[X]
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