Variance Example

library(UsingR)

## Loading required package: MASS
## Loading required package: HistData
## Loading required package: Hmisc
## Loading required package: grid
## Loading required package: lattice
## Loading required package: survival
## Loading required package: Formula
## Loading required package: ggplot2
## 
## Attaching package: 'Hmisc'
## 
## The following objects are masked from 'package:base':
## 
##     format.pval, round.POSIXt, trunc.POSIXt, units
## 
## 
## Attaching package: 'UsingR'
## 
## The following object is masked from 'package:ggplot2':
## 
##     movies
## 
## The following object is masked from 'package:survival':
## 
##     cancer

data(father.son)
x<- father.son$sheight
n<- length(x)

Interpret the number

round(c(var(x),var(x)/n,sd(x),sd(x)/sqrt(n)),2)

## [1] 7.92 0.01 2.81 0.09

var(x) mean ?????????????????????????????????????????????????????? var(x)/n, ?????????????????????????????? sd(x),??????????????????????????????????????????????????? sd(x)/sqrt(n)??????????????????????????????????????????????????????