Interpreting Box Plots with Questionnaire Data

[jophysics]

Dear all,
I need to evaluate some data from questionnaires (in the form of scale of values from 0 to 10) and I thought to use the box plots. Please, someone can provide me with some helps (references,etc) for the interpretation? In some cases, the median does not falls inside the box but it is the upper bound of the box, in other cases I have upper or lower wiskers only. What do these mean?

thank you for your help!

jo

 

[statdad]

If the median is the upper or lower end of a box then the median equals the lower or upper quartile. If you have only a whisker (say the upper whisker) than almost all of the measurements equal the upper quartile and you have one (or more?) values at the maximum.

In short, in both situations, you have good numbers of duplicated data values.