1.设随机变量X~B(10,0.2),则E(X)= ? 2.设随机变量X~U(1.7),则D 设随机变量服从X?103P0.70.20.1，则E（X）=
\u8bbe\u968f\u673a\u53d8\u91cfX~B(15,0.2),\u5219E(3X)=3*15*0.2=9 \u9700\u8981\u89e3\u91ca\u5417
\u56e0\u4e3a\u968f\u673a\u53d8\u91cf\u670d\u4eceX?103P0.70.20.1\uff0c\u6240\u4ee5E\uff08X\uff09=\uff08-1\uff09\u00d70.7+0\u00d70.2+3\u00d70.1=0.4D\uff08X\uff09=E\uff08X2\uff09-E\uff08X\uff092=\uff08-1\uff092\u00d70.7+02\u00d70.2+32\u00d70.1-\uff080.4\uff092=1.44\uff0e\u6545\u7b54\u6848\u4e3a\uff1a-0.4\uff0c1.44\uff0e
1、E(X)=np=10·0.2=2
2、
D(X)=(b-a)^2/12
=36/12
=3
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