  # quartile

## What is a Quartile?

A Quartile is a type of quantile, the intervals used in defining ranges in probability density functions of continuous random variables. In simple terms, a Quartile is the defining line between intervals within the probability density functions. While Quartiles have no inherent value or transformational properties, they are defined by a discrete value. Unlike a quantile that is defined by the area of an interval, a Quartile is defined by a discrete value.

## How does a Quartile work?

Imagine a probability density function, in which we already know the median, also defined as the second Quartile or middle value. The first quartile is the boundary line, defined by a discrete point, that separates the first half of the curve into two equal parts. Another way of thinking about this is to look at the first Quartile as defining the lowest 25% of the data. The second Quartile, the median, is the boundary between the lower, and upper, 50% of the data. The third Quartile, sometimes called the upper Quartile, defines the boundary between the upper 25% and the lower 75% of the data. Source

### Quartiles and Machine Learning

As a subset of probability density functions, quartiles are often used in neural networks and machine learning functions. For example, if one is using a neural network to analyze a set of data, it is integral in the creation of a probability density function to define and understand the boundary Quartiles that separate the quantiles containing the possible probabilities of a continuous random variable occurring.