Data Science with Python Certification Data Science with Python Unsupervised Learning Algorithms 2

Question 1

Which distance metric is most sensitive to outliers in clustering?

Accepted Answer

Euclidean distance

Answer

Euclidean distance squares differences, amplifying the effect of outliers compared to other metrics.

Question 2

In DBSCAN, what is a 'border point'?

Accepted Answer

A point within epsilon of a core point but not itself a core point

Answer

A border point is reachable from a core point but has fewer than MinPts neighbors within epsilon.

Question 3

Which Python library provides the `AgglomerativeClustering` class?

Accepted Answer

sklearn.cluster

Answer

`AgglomerativeClustering` is part of scikit-learn's `sklearn.cluster` module.

Question 4

What does the cophenetic correlation coefficient measure in hierarchical clustering?

Accepted Answer

How faithfully the dendrogram preserves pairwise distances

Answer

The cophenetic correlation coefficient compares original pairwise distances to dendrogram distances to evaluate linkage quality.

Question 5

When applying PCA, what does a negative eigenvalue indicate?

Accepted Answer

A numerical error, since covariance matrices always yield non-negative eigenvalues

Answer

Covariance matrices are positive semi-definite, so all eigenvalues must be ≥ 0; negatives indicate numerical precision errors.

Data Science with Python Certification Practice Test