ci-calculation-heights.R

> library(MASS)                  # load the MASS package 
> height.response = na.omit(survey$Height)
> n = length(height.response) 
> s = sd(height.response)        # sample standard deviation 
> SE = s/sqrt(n); SE             # standard error estimate 
[1] 0.6811677
> 
> print(paste("Standard Error:", SE))
[1] "Standard Error: 0.68116773214787"
> 
> E = qt(.975, df=n-1)*SE     # margin of error 
> 
> print(paste("Margin of Error:", E))
[1] "Margin of Error: 1.34287767542194"
> 
> xbar = mean(height.response)   # sample mean 
> xbar + c(-E, E) 
[1] 171.0380 173.7237
> 
> # OR THE EASY WAY
> 
> t.test(height.response)

	One Sample t-test

data:  height.response
t = 253.07, df = 208, p-value < 2.2e-16
alternative hypothesis: true mean is not equal to 0
95 percent confidence interval:
 171.0380 173.7237
sample estimates:
mean of x 
 172.3809