若随机变量X服从两点分布,且成功的概率p=0.5,则E(X)和D(X)分别为( )A.0.5和0.25B.0.5和0.75C.1和0.25D.1和0.75
∵X服从两点分布,
∴X的概率分布为
![](/img.php?b=https://iknow-pic.cdn.bcebos.com/242dd42a2834349be8553d33caea15ce36d3be31?x-bce-process=image/quality,q_85)
∴E(X)=0×0.5+1×0.5=0.5,
D(X)=0.52×0.5+(1-0.5)2×0.5=0.25.
故选A.
∴X的概率分布为
∴E(X)=0×0.5+1×0.5=0.5,
D(X)=0.52×0.5+(1-0.5)2×0.5=0.25.
故选A.
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