The range. An outlier is a set of data that changes the overall look of everything. Let's say you had the numbers 2, 3, 5, and 19. 19 is the outlier. To find the range, you subtract the largest number by the smallest, making the range of this set of numbers 17. If we didn't have 19, our range would be 3. The median would be 3, without the outlier, and with the outlier it would be 4. Hope this helps ;)