Current location - Education and Training Encyclopedia - University ranking - A In a university.
A In a university.
(1) Suppose that the probability of Xiao Zhang taking A, B and C is X, Y and Z respectively.

X( 1? y)( 1? z)=0.08xy( 1? z)=0. 12 1? ( 1? x)( 1? y)( 1? Z) = 0.88 x = 0.4y = 0.6z = 0.5。

So the probability of student Xiao Zhang getting an A is 0.4.

(ii) If the function f(x)=x2+ξx is an even function on r, ξ=0.

When ξ=0, it means that Xiao Zhang has chosen three courses or none.

∴p(a)=p(ξ=0)=xyz+( 1-x)( 1-y)( 1-z)=0.4×0.5×0.6+( 1-0.4)( 1-0.5)( 1-0.6)=0.24

The probability of event A is 0.24.

(iii) according to the meaning of the question, ξ = 0,2.

Then the distribution list of ξ is

ξ 0 2p0.24 0.76 ∴ξis's mathematical expectation Eξ=0×0.24+2×0.76= 1.52.