Box and Whisker Plot. Right in the middle of my top 5 Desert Island Tools is one of the most illustrative and simple graphs available to an analyst. The box and whisker plot reveals center, spread, shape and outliers. It can be used to stratify a data set and demonstrate differences in one or more levels of grouping variables.
The graphic clarity of the box and whisker plot provide the analyst with a quick and easy way to visualize data and allow for exploration of critical factors, main effects, and even interactions. For example, differences in cycle time by shift, day, operator and or product can be easily explored using this graph. This is truly a graph that will raise questions as well as answer them.
When the questions you are trying to answer revolve around distribution shape, center and spread, there is no tool quite so well suited as the box and whisker plot.