Finding a Confidence Interval using RStudio

These instructions assume that you’ve already installed the necessary package and that you’ve imported and attached your data file. 

To find a confidence interval in RStudio, you will invoke the following command: 

t.test(variable, conf.level = 0.95)$conf.int

In this example, we are finding a 95% confidence interval of the intended variable. 

For example, let’s say you have a vector of data called ‘x’ and you want to find the 95% confidence interval for the population mean.

First, we’ll create the vector x and define what data it contains: 

x <- c(23, 17, 18, 21, 19, 22, 20, 24, 16, 25)

Next, we’ll ask RStudio to determine the 95% confidence interval for x:

t.test(x, conf.level = 0.95)$conf.int

The output will look something like the following: 

[1] 18.68844 23.31156
attr(,”conf.level”)
[1] 0.95

So, we are 95% confident that the true population mean of x will lie between 18.68844 and 23.31156.