设<imgwidth="112"height="21"v:shapes="_x0000_i1027"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb10.files/image004.png">,即<imgwidth="13"height="15"v:shapes="_x0000_i1028"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb10.files/image006.png">服从参数为<imgwidth="15"height="19"v:shapes="_x0000_i1029"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb10.files/image008.png">的泊松分布,则<imgwidth="51"height="44"v:shapes="_x0000_i1030"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb10.files/image010.png">()
②
<imgwidth="15"height="18"v:shapes="_x0000_i1031"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb10.files/image012.png">