单选题 Which of the following is NOT an assumption of the binomial distribution?

A. The trials are independent.
B. Random variable X is discrete.
C. The expected value is a whole number.

【正确答案】 C

【答案解析】The expected value is n×p. A simple example shows us that the expected value does not have to be a whole number : n=5, p=0.5, n×p=2.5. All the other conditions are necessary for the binomial distribution.