The Spread or Dispersion of a Batch
Some batches of numbers are very tightly bunched together while others are much more spread out. This property is referred to in exploratory data analysis as spread (or in more traditional statistical terms as dispersion), and it is often an informative characteristic of a batch to which you should pay attention. Just as it is convenient to have a numerical index for the level or center of a batch, it is also convenient to have a numerical index for the spread, or dispersion, of a batch. Once again there are several different numerical indexes that behave differently and are thus used in different circumstances.