问题
单项选择题
For a binomial random variable B(n=12, p=0.5), find out the mean and variance. Mean Variance ()①A. 6 3 ②B. 7 3.5 ③C. 8 4
A. ①
B. ②
C. ③
答案
参考答案：A
解析：
A binomial random variable has an expected value or mean equal to np and variance equal to np (1-p). Mean=12×0.5=6; variance 12×0.5×(1-0.5)=3.