NO.PZ2017092702000090
问题如下：
X is a discrete random variable with possible outcomes X = {1,2,3,4}. Three functions f(x), g(x), and h (x) are proposed to describe the probabilities of the outcomes in X.
The conditions for a probability function are satisfied by:
选项：
A.f(x).
B.g(x).
C.h(x)
解释：
B is correct.
The function g(x) satisfies the conditions of a probability function. All of the values of g(x) are between 0 and 1, and the values of g(x) all sum to 1.
本题在于求三个函数中哪一个符合概率函数的定义。这就要满足两个条件:
第一，所有的概率的范围在0~1之间，这样f(x)就不满足条件了；
第二，每一列的四个概率加起来应该等于1，这样h(x)就不符合条件了。
所以选B
如题
