Here is a lesson plan that takes an interesting approach to analyzing data using box and whisker plots.  By using an applet that dynamically generates Venn diagrams, the class forms a strategy/algorithm for guessing the rule that fits the Venn diagram. Pupils test their algorithm on additional Venn diagrams as they continue to guess rules and gather data, which is then used to create box and whisker plots.  The lesson plan provides many opportunities for learners to discuss and defend their thinking.