问题
单项选择题
Which of the following is NOT a probability distribution（）
A. Flip a coin: P(H)=P(T)=0.5.
B. Roll an irregular die: P(1)=P(2)=P(3)=P(4)=0.2 and P(5)=P(6)=0.1.
C. Zeta Corp. : P(dividend increases)=0.60, P(dividend decreases)=0.30.
答案
参考答案：C
解析：
All the probabilities must be listed. In the case of Zeta Corp. the probabilities do not sum to one.