Exercise

# Confidence interval

**The confidence interval** is **a range** in which we suspect the population's mean to land.

You may expect questions on confidence intervals if your future project touches *behavioral* or *medical science*, *politics*, or *advertising*.

In this exercise, you'll practice computing confidence intervals using the `sleep`

dataset from the datasets package.
The dataset contains data on the effect of two drugs on ten patients.
The effect is measured as an increase in hours of sleep compared to control, which is stored in the `extra`

column.

A confidence interval is stored in the `conf.int`

component of an object created with `t.test()`

.

You can retrieve it like this:

```
t.test(x)$conf.int
```

**Watch out!** To run a t-test, your data needs to be **normally distributed**.

Instructions 1/3

## Question

If we increase the confidence level, how does the confidence interval change?