The Level or Center of a Batch
As we saw in Chapter 1, the numbers in a batch often bunch together. If we compare two related batches of numbers, the principal bunch in one batch may well have higher numbers in general than the principal bunch in the other batch. We say that such batches have different levels or centers. It is convenient to use a numerical index of the level for such comparisons. The several such indexes in common use are traditionally referred to as measures of central tendency.