19. (5%) A traffic light can be in one o..-阿摩線上測驗
19. (5%) A traffic light can be in one of the three states: Green (G), Red (R), and Yellow
(Y). The light changes in a random fashion. At any one time, the light can be in only
one state. The experiment consists of observing the state of the light.
Let a random variable X(') be defined as follows: X(G)=-1, X(R)=0,
X(Y) = π; assume that P(G) = P(Y) = 0.5 P(R), what is P(X ≦ 3)?
(A)1/4
(B) 1/2
(C) 3/4
(D)1
(E) 0