Question

大学概率分布题目

Answer 1

f(x)

=2x                 ; 0<x<1

=0                  ; elsewhere

P(X≤1/2)

= ∫(0->1/2) 2x dx

=[x^2]|(0->1/2)

=1/4

P(Y=2)

=(3C2)(1/4)^2. (3/4)

=3(1/16)(3/4)

=9/64

ans :A

追问

还可以问一个吗

追答

P(|X|>a)
=P(X>a or Xa) +P(X<-a)
=[1-P(X≤a)] +[ 0.5 -P(-a<X<0) ]
=[1- F(a) ] + [ 0.5 -( F(a) -0.5) ]
=2-2F(a)
=2[ 1- F(a) ]
ans : D