Course Content

# Learning Statistics with Python

2. Mean, Median and Mode with Python

3. Variance and Standard Deviation

4. Covariance vs Correlation

Learning Statistics with Python

## t-test Mathematically

The task of the t-test is to determine whether the difference between the two samples' means is significant. What should we take into consideration to perform it?

- Obviously, we should consider the
**difference between the means**itself.

- As shown in the image below, the
**variance**matters too!

- Also, the
**size**of each sample should be taken into consideration.

To account for the **difference between the means**, we simply calculate that difference:

The situation becomes more complex when it comes to **variance**. The t-test assumes that the variance is equal for both samples. We will delve deeper into this in the *t-test assumptions* chapter. To estimate the variance from two samples, the **pooled variance** formula is applied:

And to account for the **size**, we need sample sizes:

Let's put it all together into **t statistic**.

You may have noticed that sample sizes are not used in the most intuitive manner. However, this approach ensures that **t** follows the **t-distribution**, as we'll explore in the next chapter.

What sample properties does the t-test take into account?

## Select a few correct answers

Everything was clear?