单选题 Which of the following qualifies as a cumulative distribution function? A. F(1)=0.5, Y(2)=0.25, F(3)=0.25. B. F(1)=0, F(2)=0.5, F(3)=0.5, F(4)=0. C. g(1)=0, F(2)=0.25, F(3)=0.50, F(4) =1.

【正确答案】 C

【答案解析】Because a cumulative probability function defines the probability that a random variable takes a value equal to or less than a given number, for successively larger numbers, the cumulative probability values must stay the same or increase.