Corbet et al. (1970) report a study of water voles (genus Arvicola) in which the aim was to compare British populations of these animals with those in Europe, to investigate whether more than one species might be present in Britain. The original data consisted of observations of the presence or absence of 13 characteristics in about 300 water vole skulls arising from six British populations and eight populations from the rest of Europe. Table 17.1 gives a distance matrix derived from the data as described in Corbet et al. (1970). Romesburg (1984) gives a set of data that shows the number of times 15 con-
gressmen from New Jersey voted differently in the House of Representatives on 19 environmental bills. Abstentions are not recorded, but two congressmen abstained more frequently than the others, these being Sandman (nine abstentions) and Thompson (six abstentions). The data are available in Table 17.2 and of interest is if party affiliations can be detected.