问题如下:
The stock of AAA company has a 30% probability to rise every year, if every annual trial is independent from each other, the probability that the stock will rise more than 1 time in the next 3 years is:
选项:
A.0.145
B.0.216
C.0.377
解释:
B is correct. Based on the corresponding formula:
, n = 3 and p = 0.30.
p(2)=\frac{3!}{(3-2)!2!}\times0.3^2(1-0.3)^1=\left(3\right)\left(0.09\right)\left(0.7\right)=0.189\).
The required probability is: p(2) + p(3) = 0.189 + 0.027 = 0.216
这道题该用哪个公式解呢?