As suggested by the next two investigations, one way to use a box and whisker plot is to look for unexpected features in our data that merit attention, such as an oddly shaped distribution of results or an unusually large or an unusually small result for a variable.
Investigation 7. The box and whisker plot in Figure 1 is perfectly symmetrical in that each side of the box is two units from the box’s middle line, and each whisker is six units from the nearest edge of the box. What does this symmetry suggest about how the results are distributed? Is the actual distribution of the 30 results perfectly symmetrical? If no, is this a problem?
Investigation 8. In Figure 1 we see that the result for sample 22 falls outside the range of values included within the whiskers. Why might a result that falls outside the whiskers concern us? Does the presence of this particular point suggest a problem? How might your response change if this sample’s reported value is 0 yellow M&Ms? How might your response change if this sample’s reported value is 45 yellow M&Ms?