Silhouette Score and Cluster Evaluation Quiz

Answers and explanations appear as you take the quiz.

1. With a=2 and b=5, what is the silhouette coefficient (b-a)/max(a,b)?
   • 0.6
   • -0.6
   • 0.4
   • 1.5
2. A point has a=4 and b=3. What does its negative silhouette indicate?
   • Its assigned cluster has zero observations
   • It is, on average, closer to another cluster under the chosen distance
   • The global score must be negative
   • The feature scaling is proven correct
3. What does a silhouette near zero commonly suggest for one observation?
   • Its class label is known
   • It is perfectly separated from all clusters
   • It lies near a boundary between its own and another cluster
   • The clustering has one cluster only
4. Which direction is generally preferred for the Davies-Bouldin index?
   • A value matching the silhouette range
   • Higher values
   • Exactly zero for every useful partition
   • Lower values
5. Why should raw Davies-Bouldin and Calinski-Harabasz values not be compared directly?
   • Both are probability estimates between zero and one
   • They use different formulas, scales and preferred directions
   • They require identical units by definition
   • One is always the reciprocal of the other
6. Why can an average silhouette hide a cluster-specific problem?
   • Every sample receives a different formula
   • Silhouette uses only labels and no distances
   • A sample-weighted mean can mask weak values in a smaller group
   • A negative value is omitted automatically
7. What does a high silhouette score fail to establish by itself?
   • That labels were assigned
   • That within and between distances were calculated
   • That the chosen metric was used
   • That the clusters are useful for the downstream task
8. When is the silhouette score undefined in common implementations?
   • For degenerate labelings with one cluster or one cluster per sample
   • Whenever the average coefficient is positive
   • When a cluster has two observations
   • When distances use standardized features