diff --git a/lectures/lln_clt.md b/lectures/lln_clt.md index 291690e0..83f21d43 100644 --- a/lectures/lln_clt.md +++ b/lectures/lln_clt.md @@ -51,6 +51,9 @@ will converge to their population means. Let's see an example of the LLN in action before we go further. +```{prf:example} +:label: lln_ex_ber + Consider a [Bernoulli random variable](https://en.wikipedia.org/wiki/Bernoulli_distribution) $X$ with parameter $p$. This means that $X$ takes values in $\{0,1\}$ and $\mathbb P\{X=1\} = p$. @@ -68,6 +71,7 @@ $$ \mathbb E X = 0 \cdot \mathbb P\{X=0\} + 1 \cdot \mathbb P\{X=1\} = \mathbb P\{X=1\} = p $$ +``` We can generate a draw of $X$ with `scipy.stats` (imported as `st`) as follows: @@ -369,7 +373,8 @@ The LLN fails to hold here because the assumption $\mathbb E|X| < \infty$ is vio The LLN can also fail to hold when the IID assumption is violated. -For example, suppose that +```{prf:example} +:label: lln_ex_fail $$ X_0 \sim N(0,1) @@ -384,6 +389,7 @@ $$ $$ Therefore, the distribution of $\bar X_n$ is $N(0,1)$ for all $n$! +``` Does this contradict the LLN, which says that the distribution of $\bar X_n$ collapses to the single point $\mu$? @@ -439,9 +445,9 @@ n \to \infty Here $\stackrel { d } {\to} N(0, \sigma^2)$ indicates [convergence in distribution](https://en.wikipedia.org/wiki/Convergence_of_random_variables#Convergence_in_distribution) to a centered (i.e., zero mean) normal with standard deviation $\sigma$. -The striking implication of the CLT is that for **any** distribution with +The striking implication of the CLT is that for any distribution with finite [second moment](https://en.wikipedia.org/wiki/Moment_(mathematics)), the simple operation of adding independent -copies **always** leads to a Gaussian(Normal) curve. +copies always leads to a Gaussian(Normal) curve. @@ -599,7 +605,7 @@ $$ $$ where $\alpha, \beta, \sigma$ are constants and $\epsilon_1, \epsilon_2, -\ldots$ is IID and standard norma. +\ldots$ are IID and standard normal. Suppose that