A major problem facing persons working with masses of data is visualizing the situation represented by those data. Arranging the data into arrays or frequency distributions and the construction of frequency polygons, histograms, or bar graphs help immensely, but in many cases it would be advantageous to be able to collapse the set of data items into a single representative value. A number of such single-value representations have been developed. Collectively they are
sures of central tendency
. Each of these averages has its own characteristics, and situations exist where each is the appropriate one to use.