Understanding non-parametric data

Non-parametric data is data that does not follow a normal or well-known distribution. Let’s briefly cover what that means. To put it simply, if you visualize the frequency of a numerical variable, you will often have the most common values higher in the middle. As you move away from the middle, the frequency decreases as you get larger or smaller. This creates what is commonly known as a bell curve or a normal distribution, as depicted in Figure 4.9:

Figure 4.9 – Normal distribution

In statistics, a distribution can be used to predict the probability that a new value will be any specific number. We will talk more about distributions later in this book. For now, know that there are a few distributions that are common and well-understood, such as the normal distribution depicted in the preceding screenshot.

Non-parametric data does not follow any of the common distributions. To put it another way, the data...