Understanding the box plot chart

A box plot is a technical chart that shows data samples in terms of the shape of distribution. Before we can create a box plot chart, we need to understand the basic structure and concept. The following diagram illustrates the structure of a box plot:

In order to find out the percentile values, the entire data sample needs to be sorted first. Basically, a box plot is composed of top and bottom whisker values, first (Q1) and third (Q3) quartile values, and the median. The quartile Q1 represents the median value between the 50th percentile and the minimum data. Quartile Q3 works in a similar fashion but with maximum data. For data with a perfectly normal distribution, the box plot will have an equal distance between each section.

Strictly speaking, there are other types of box plot that differ in how much the percentiles of both whiskers cover. Some use the definition of 1.5 times the inter-quartile range, that is, 1.5 * (Q3 - Q1), or standard deviation. The...