# Demonstration of the Central Limit Theorem

### Yihui Xie & Lijia Yu / 2017-04-04

First of all, a number of obs observations are generated from a certain distribution for each variable $$X_j$$, $$j = 1, 2, \cdots, n$$, and $$n = 1, 2, \cdots, nmax$$, then the sample means are computed, and at last the density of these sample means is plotted as the sample size $$n$$ increases (the theoretical limiting distribution is denoted by the dashed line), besides, the P-values from the normality test shapiro.test are computed for each $$n$$ and plotted at the same time.

As long as the conditions of the Central Limit Theorem (CLT) are satisfied, the distribution of the sample mean will be approximate to the Normal distribution when the sample size n is large enough, no matter what is the original distribution. The largest sample size is defined by nmax in ani.options.

library(animation)
ani.options(interval = 0.1, nmax = 150)
op = par(mar = c(3, 3, 1, 0.5), mgp = c(1.5, 0.5, 0), tcl = -0.3)
clt.ani(type = "s")

par(op)

## other distributions: Chi-square with df = 5 (mean = df, var
## = 2*df)
f = function(n) rchisq(n, 5)
clt.ani(FUN = f, mean = 5, sd = sqrt(2 * 5))