Determine which of the following statements is/are true.

• The number of clusters must be pre-specified for both K-means and hierarchical clustering.
• The K-means clustering algorithm is less sensitive to the presence of outliers than the hierarchical clustering algorithm.
• The K-means clustering algorithm requires random assignments while the hierarchical clustering algorithm does not.

• I only
• II only
• III only
• I, II and II
• The correct answer is not given by (A), (B), (C), or (D)

Determine which of the following statements is applicable to K-means clustering and is not applicable to hierarchical clustering.

• If two different people are given the same data and perform one iteration of the algorithm, their results at that point will be the same.
• At each iteration of the algorithm, the number of clusters will be greater than the number of clusters in the previous iteration of the algorithm.
• The algorithm needs to be run only once, regardless of how many clusters are ultimately decided to use.
• The algorithm must be initialized with an assignment of the data points to a cluster.
• None of (A), (B), (C), or (D) meet the meet the stated criterion.

You are given a set of n observations, each with p features. Determine which of the following statements is/are true with respect to clustering methods.

• The n observations can be clustered on the basis of the p features to identify subgroups among the observations.
• The p features can be clustered on the basis of the n observations to
identify subgroups among the features.
• Clustering is an unsupervised learning method and is often performed as part of an exploratory data analysis.

• None
• I and II only
• I and III only
• II and III only
• The correct answer is not given by (A), (B), (C), or (D).

Determine which of the following statements is/are true about clustering methods:

• If K is held constant, K-means clustering will always produce the same cluster assignments.
• Given a linkage and a dissimilarity measure, hierarchical clustering will always produce the same cluster assignments for a specific number of clusters.
• Given identical data sets, cutting a dendrogram to obtain five clusters produces the same cluster assignments as K-means clustering with K = 5.

• I only
• II only
• III only
• I, II and III
• The correct answer is not given by (A), (B), (C), or (D).

Determine which of the following statements about clustering is/are true.

• Cutting a dendrogram at a lower height will not decrease the number of clusters.
• K-means clustering requires plotting the data before determining the number of clusters.
• For a given number of clusters, hierarchical clustering can sometimes yield less accurate results than K-means clustering.

• None
• I and II only
• I and III only
• II and III only
• The correct answer is not given by (A), (B), (C), or (D).

Determine which of the following statements is NOT true about clustering methods.

• Clustering is used to discover structure within a data set.
• Clustering is used to find homogeneous subgroups among the observations within a data set.
• Clustering is an unsupervised learning method.
• Clustering is used to reduce the dimensionality of a dataset while retaining explanation for a good fraction of the variance.
• In K-means clustering, it is necessary to pre-specify the number of clusters.