Suppose that last week, the average amount of time spent per visitor to a website was `25`

minutes. This week, the average amount of time spent per visitor to a website was `29`

minutes. Did the average time spent per visitor change (i.e. was there a statistically significant bump in user time on the site)? Or is this just part of natural fluctuations?

One way of testing whether this difference is significant is by using a Two Sample T-Test. A *Two Sample T-Test* compares two sets of data, which are both approximately normally distributed.

The null hypothesis, in this case, is that the two distributions have the same mean.

You can use R’s `t.test()`

function to perform a Two Sample T-Test, as shown below:

results <- t.test(distribution_1, distribution_2)

When performing a Two Sample T-Test, `t.test()`

takes two distributions as arguments and returns, among other information, a p-value. Remember, the p-value let’s you know the probability that the difference in the means happened by chance (sampling error).

### Instructions

**1.**

We’ve created two distributions representing the time spent per visitor to BuyPie.com last week, `week_1`

, and the time spent per visitor to BuyPie.com this week, `week_2`

.

Find the means of these two distributions. Store them in `week_1_mean`

and `week_2_mean`

. View both means.

**2.**

Find the standard deviations of these two distributions. Store them in `week_1_sd`

and `week_2_sd`

. View both standard deviations.

**3.**

Run a Two Sample T-Test using the `t.test()`

function.

Save the results to a variable called `results`

and view it. Does the p-value make sense, knowing what you know about these datasets?

# Take this course for free

By signing up for Codecademy, you agree to Codecademy's Terms of Service & Privacy Policy.