The distribution of a single group of numbers can be described by the five-number summary, which consists of the median, the two quartiles, and the two extremes. These numbers are ``landmarks'' in the distribution and provide a compact description of a data set. The median indicates the centre of the data. The quartiles give an indication of variability: their difference is the interquartile range. The extremes give bounds for the data set and can show extreme outliers. The distances of the median to the quartiles give an indication of whether the distribution is symmetrical or skewed. 
In this thesis, when summarising a set of data, the five-number summary will be presented along with the size of the data set, the mean and the standard deviation.