ABSTRACT
In this chapter, the authors look at techniques for dealing with sets of data, rather than single numbers. The statistics (for describing interval data) are all based on adding or subtracting values. Also, if data are interval but very strangely distributed with extreme values, the sample mean and variance might be a poor summary of most of the data points (because they are influenced by extreme values). In such case, the readers might wish to have an alternative way of summarizing data. The median provides an alternative measure of central tendency to the sample mean that can be calculated for ordinal data or interval data. The median is middle measurement in a set of data; that is, there are just as many values larger than the median as there are smaller. Graphical displays of information are very helpful in terms of quickly conveying information. However, if not drawn carefully such figures can just as quickly give a misleading impression.
