Database Reference
In-Depth Information
The small dots represent the students corresponding to the appropriate cluster by
assigned color: red, blue, or green. In general, the plots indicate the three clusters
of students: the top academic students (red), the academically challenged students
(green), and the other students (blue) who fall somewhere between those two
groups. The plots also highlight which students may excel in one or two subject
areas but struggle in other areas.
Figure 4.6
Plots of the identified student clusters
Assigning labels to the identified clusters is useful to communicate the results of
an analysis. In a marketing context, it is common to label a group of customers as
frequent shoppers or big spenders. Such designations are especially useful when
communicating the clustering results to business users or executives. It is better to
describe the marketing plan for big spenders rather than Cluster #1.
4.2.4 Diagnostics
The heuristic using WSS can provide at least several possible k values to consider.
When the number of attributes is relatively small, a common approach to further
refine the choice of k is to plot the data to determine how distinct the identified
clusters are from each other. In general, the following questions should be
considered.
• Are the clusters well separated from each other?
• Do any of the clusters have only a few points?
• Do any of the centroids appear to be too close to each other?
