**The whiskers** add 1.5 times the IQR to the 75 percentile (aka Q3) and subtract 1.5 times the IQR from the 25 percentile (aka Q1). The whiskers should include 99.3% of the data if from a normal distribution. So the 6 foot tall man from the example would be inside the whisker but my 6 foot 2 inch girlfriend would be at the top whisker or pass it.

**The Line** - Shows the median of the data

**The Notch** - displays the a confidence interval around the median which is normally based on the median +/- 1.57 x IQR/sqrt of n. According to Graphical Methods for Data Analysis (Chambers, 1983) although not a formal test the, if two boxes' notches do not overlap there is ‘strong evidence’ (95% confidence) their medians differ. **Note **Here are the pages from the book. **Citation** Chambers, John M., William S. Cleveland, Beat Kleiner, and Paul A. Tukey. "Comparing Data Distributions." In Graphical Methods for Data Analysis, 62. Belmont, California: Wadsworth International Group;, 1983. ISBN 0-87150-413-8 International ISBN 0-534-98052-X

**Note:** few software programs can make notched box plots (R and ProUCL for example). The notched box plots in this document were all generated in R which requires time to learn. The following web page allows you to enter data and generate notched box plots but for __noncommercial__ use wessa.net/rwasp_notchedbox1.wasp R can also make notch box plots. Here is how to do it in R.

The image below show the relationship of notched box plot and data distribution, variance, and populations.