Silhouette Plot
Select this to create a silhouette plot for the clustering. This plot indicates the strength of cluster membership for each observation. For each observation i, a bar is drawn, representing the silhouette width s(i) of the observation. Observations are grouped per cluster, starting with cluster 1 at the top. Observations with a large s(i) (almost 1) are very well clustered, a small s(i) (around 0) means that the observation lies between two clusters, and observations with a negative s(i) are probably placed in the wrong cluster.