A QQ plot helps us see if the data fits a distribution.

Let’s take Normal distribution as an example:

## Steps to do a QQ plot for normal distribution §

### Step 4: Plot the QQ plot §

Get the x coordinate from the line in normal distribution, and get y coordinate from the data set. For each quantile, we draw a dot and we will get a QQ graph.

### Interpret the results §

If most dots fit a straight line, the data is normally distributed. If many of them did not fit, we should consider other distributions.

## Compare two dataset with QQ plot §

QQ plot can be used to compare datasets and see if they have similar distribution.

### Example: Compare dataset to another smaller dataset §

The new dataset only has 4 quartiles.

The steps are similar. We take the dataset with the smaller size and determine the another data set with the same number of quantile. Then get the x from the new dataset, and y from original dataset.

Once we get the dots, we can add a straight line to see how fit it is. If it fits well, meaning the two datasets similar distributions.