Comparing Batches

Abstract

We have already compared batches with back-to-back stem-and-leaf plots, but there are quicker and more effective tools for graphically comparing batches. The numerical indexes of the center and spread of a batch that we have discussed in the last two chapters provide the basis for such tools. A standard way of plotting some of these indexes in exploratory data analysis is called the box-and-dot plot (or the box-and-whisker plot). The box-and-dot plot could, in theory, be based on any of the indexes of center and spread, but in practice the median and the midspread are used. This is such standard practice that a box-and-dot plot is automatically taken to represent the median and midspread, and this convention should not be violated.