I am doing k-means clustering using fastclus and am getting negative and decreasing CCC values as I increase the number of clusters. The following link says the distribution might be unimodal and long tailed.   http://support.sas.com/kb/22/540.html   What does this mean? Is this talking about the variables I am clustering on or the distribution of the CCC value itself? I am going to try non-parametric clustering to see if that gives me better results. Can anybody suggest anything else apart from that?    Thanks ... View more