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Weak Law of Large Number

  • Expectation of the Sample Mean: E[Xnโ€พ]\mathbb{E}[\overline{X^n}]
  • Variance of the Sample Mean: V[Xnโ€พ]\mathbb{V}[\overline{X^n}]

Sample Mean ฮธ^n\hat{\theta}_n is converging to Population Mean ฮธ\theta: limโกnโ†’โˆžE[(ฮธ^nโˆ’ฮธ)2]=0\lim\limits_{n \to \infty} \mathbb{E}[(\hat{\theta}_n - \theta)^2] = 0

limโกnโ†’โˆžV[ฮธ^n]+(E[ฮธ^n]โˆ’ฮธ)2)=0\lim\limits_{n \to \infty} \mathbb{V}[\hat{\theta}_n] + (\mathbb{E}[\hat{\theta}_n] - \theta)^2) = 0

limโกnโ†’โˆžฯƒx2n+(ฮผxโˆ’ฮผx)2=0\lim\limits_{n\to\infty} {\sigma_x^2 \over n} + (\mu_x - \mu_x)^2 = 0

ฮธ^nโ†’ฮธ\hat{\theta}_n \to \theta

โˆ€ฯต>0\forall \epsilon > 0, limโกnโ†’โˆžP(โˆฃฮธ^nโˆ’ฮธ)โˆฃ>ฯต)=0\lim\limits_{n \to \infty} P(|\hat{\theta}_n - \theta)| > \epsilon) = 0

limโกnโ†’โˆžP(โˆฃxnโ€พโˆ’ฮผxโˆฃ>ฯต)โ‰คlimโกnโ†’โˆžฯƒx2nฯต2\lim\limits_{n \to \infty} P(|\overline{x_n} - \mu_x| > \epsilon) \leq \lim\limits_{n \to \infty} {\sigma_x^2 \over {n \epsilon^2}}

MIโ€‹

xโ‰ฅ0,cโˆˆR+,E[X]<โˆžx \geq 0, c \in \mathbb{R}^+, \mathbb{E}[X] < \infty

P(X)โ‰ฅC)โ‰คE[X]CP(X) \geq C) \leq {\mathbb{E}[X] \over C}

CIโ€‹

ฯƒx2<โˆž\sigma_x^2 < \infty

P(โˆฃxโˆ’ฮผxโˆฃ>ฯต)โ‰คฯƒx2ฯต2P(|x - \mu_x| > \epsilon) \leq {\sigma_x^2 \over \epsilon^2}