Probability
# Total Probability
$P\left( A\right) =P\left( B_{1}\right) P\left( A| B_{1}\right) +\ldots +P\left( B_{n}\right) P\left( A| B_{n}\right)$
$S=B_{1}\cup \ldots \cup B_{n}$
$B_{1}\cup \ldots \cup B_{n}$ 为划分
=>
$P\left( A\right) =P\left( AS\right) =P\left( A\cap \left( B_{1}\cup \ldots \cup B_{n}\right) \right)$
# 概率密度

变量大写表示变量本身,变量小写表示取值
函数小写表示概率密度(概率的取值),大写表示分布函数(概率的累加)
- N 维随机变量概率
- Bayes Theorem
- Series
- Expectation
- Poisson distribution
- 参数估计
- 方差:D(X) = Var(X) = $E{[X - E(x)]^{2}}$ = $E(X^{2})- E^{2}(X)$
- 协方差/标准差:$\sqrt{D(X)}$
- 相关系数:正态分布,泊松分布