Practical Data Analysis with JMP®

Outlier Box Plots

Now that we've discussed the five-number summary, we can interpret the box plot just above the histogram back in Figure 3.7. The key to interpreting an outlier box plot is to understand that it is essentially a diagram of the five-number summary.

In a box plot there is a rectangle with an intersecting line. Two edges of the rectangle are located at the first (Q1) and third (Q3) quartile values, and the line is located at the median. In other words, the rectangular box spans the interquartile range (IQR). Extending from the ends of the box are two lines (whiskers). In a distribution that is free of outliers, the whiskers reach ...