In Exploratory Data Analysis (EDA), data can be organized using a stem and leaf plot. (See Chapter 2.) The measure of central tendency used in EDA is the median. The measure of variation used in EDA is the interquartile range Q3-Q1. In EDA the data are represented graphically using a boxplot (sometimes called a box and whisker plot). The purpose of exploratory data analysis is to examine data to find out what information can be discovered about the data, such as the center and the spread. Exploratory data analysis was developed by John Tukey and presented in his book Exploratory Data Analysis (Addison-Wesley, 1977).