Measures of Dispersion

Measures of dispersion are meant to describe variety in values.  How many different answers/categories/values are there and how frequent are each of them?  How you describe variety depends on what sort of data you are dealing with.  If your data is nominal or ordinal, you don't have many good options for describing dispersion.  For the most part you should just use percentages to describe 

For example, if you look at 500 different television ads and you want to describe how long a typical ad runs on television, you would use a measure of central tendency.  There are many measures of central tendency but the three most commonly used are the mean, median, and mode.  Which measure you use depends on the type of data you are trying to describe.

• Percentages

• Range

• Interquartile Range (IQR)

• Variance and Standard Deviation