Most people do not have difficulty comparing a single number with a single number, for example, noting that the median of one set of counts is greater than the median of another, or comparing one upper quartile with another. Some people, though, may have difficulty in comparing the distribution of one set of counts with the distribution of another.
To compare one Five-Number Summary with another in the proper way requires a composite comparison of five numbers to five numbers; you must think beyond single-number comparisons. The box plots help to clarify this comparison, especially the variation within a group as indicated by the range and the interquartile range.
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