Question

若X的分布列为:

X	0	1
P	p	q

其中P∈（0,1）,则(    )

A.EX=p DX=p³                              B.EX=p DX=p²

C.EX=q DX=q²                              D.EX=1-p DX=p-p²

Answer 1

解析：由于p+q=1,所以q=1-p.

从而EX=0×p+1×q=q=1-p,

DX=［0-(1-p)］²p+［1-(1-p)］²q

=(1-p)²p+p²(1-p)

=p-p².

答案：D