求题详细解答

设随机变量X~N(10, 4),求P{X>12},P{|X|<6},P{|X-10|<2},P{10<X<13}.

X~N(10, 4)
Z=(X-10)/2 ~N(0,1)
P(X>12)
=P(Z>(12-10)/2
=P(Z>1)
P(|X|<6)

=P(-6<X<6)
=P( (-6-10)/2<Z<(6-10)/2)
=P( -8<Z<-2)
P(|X-10|<2)

=P(-2<X-10<2)
=P(8<X<12)
=P((8-10)/2<Z<(12-10)/2)
=P(-1<Z<1)
P(10<X<13)
=P((10-10)/2<Z<(13-10)/2)
=P(0<Z<1.5)
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