Deck 20: Cluster Analysis

Question 1

Choice of a clustering method and choice of a distance measure are interrelated.

Answer 1

True

Question 2

Clustering should be done on samples of at least 300 or more.

Answer 2

False

Question 3

The primary objective of cluster analysis is to classify objects into relatively homogeneous groups.

Answer 3

True

Question 4

Nonhierarchical clustering is faster than hierarchical methods.

Question 5

In the TwoStep procedure,the euclidean measure can be used only when all of the variables are ordinal.

Question 6

In cluster analysis,the set of variables selected should describe the similarity between objects in terms that are relevant to the marketing research problem.

Question 7

The centroid method is a variance method of hierarchical clustering in which the distance between two clusters is the distance between their centroids (means for all the variables).

Question 8

The parallel threshold method differs from the other two non-hierarchical clustering procedures in that the objects can later be reassigned to clusters to optimize an overall criterion.

Question 9

Cluster analysis does not classify variables as dependent or independent.

Question 10

Most clustering methods are relatively complex procedures that are supported by an extensive body of statistical reasoning.

Question 11

The complete linkage method of hierarchical clustering is based on the minimum distance or the nearest neighbor approach.

Question 12

Use of different distance measures may lead to different clustering results.Hence,it is advisable to use different measures and compare the results.

Question 13

The dendrogram is read from right to left.

Question 14

Cluster analysis is the obverse of factor analysis in that it reduces the number of objects,not the number of variables,by grouping them into a much smaller number of clusters.

Question 15

The TwoStep cluster analysis procedure can automatically determine the optimal number of clusters by comparing the values of a model-choice criteria across different clustering solutions.

Question 16

Cluster analysis requires prior knowledge of the cluster or group membership for each object or case included to develop the classification rule.

Question 17

In cluster analysis,objects with larger distances between them are more similar to each other than are those at smaller distances.

Question 18

Measuring similarity in terms of distance between pairs of objects is the most common approach used in cluster analysis for grouping similar objects together.

Question 19

If cluster analysis is used as a general data reduction tool,subsequent multivariate analysis can be conducted on the clusters rather than on the individual observations.

Question 20

The average linkage method of hierarchical clustering is preferred to the single and complete linkage methods.

Question 21

In hierarchical clustering,the solution may depend on the order of cases in the data set.

Question 22

Formal procedures for assessing the reliability and validity of clustering are simple and should be undertaken.

Question 23

The ________ are the initial starting points in nonhierarchical clustering.

A) factor loadings
B) factor scores
C) cluster centers
D) cluster centroids

Question 24

The most important part of ________ is selecting the variables on which clustering is based.

A) interpreting and profiling clusters
B) assessing the validity of clustering
C) selecting a clustering procedure
D) formulating the clustering problem

Question 25

One method of assessing reliability and validity of clustering is to use different methods of clustering and compare the results.

Question 26

It is helpful to profile the clusters in terms of variables that were not used for clustering.

Question 27

To reduce the number of variables,a large set of variables can often be replaced by the set of cluster components.

Question 28

It is possible to obtain information on cluster membership of cases via the icicle plot if the number of clusters is specified.

Question 29

Which statement is not true about cluster analysis?

A) Objects in each cluster tend to be similar to each other and dissimilar to objects in the other clusters.
B) Groups or clusters are suggested by the data,not defined a priori.
C) Cluster analysis is also called classification analysis or numerical taxonomy.
D) Cluster analysis is a technique for analyzing data when the criterion or dependent variable is categorical and the independent variables are interval in nature.

Question 30

Cluster analysis has been used in marketing for all of the purposes below except ________.

A) determining how strongly sales are related to advertising expenditures
B) identifying new product opportunities by clustering brands and products so that competitive sets within the market can be determined
C) segmenting the market based on benefits sought from the purchase of a product
D) selecting test markets

Question 31

Clustering should be done on samples of ________ or more.

A) 50
B) 100
C) 200
D) 300

Question 32

Principal components are usually easier to interpret than the cluster components.

Question 33

In non-hierarchical clustering,the F test is only descriptive.Because the cases or objects are systematically assigned to clusters to maximize differences on the clustering variables,the resulting probabilities should not be interpreted as testing the null hypothesis of no differences among clusters.

Question 34

A ________ is a lower-triangle matrix containing pairwise distances between objects or cases.

A) similarity/distance coefficient matrix
B) classification matrix
C) factor matrix
D) correlation matrix

Question 35

Most ________ methods are heuristics based on algorithms.

A) analysis of variance
B) discriminant analysis
C) factor analysis
D) clustering

Question 36

The centroids represent the mean values of the objects contained in the cluster on each of the variables.

Question 37

Which method of analysis does not classify variables as dependent or independent?

A) cluster analysis
B) regression analysis
C) analysis of variance
D) discriminant analysis

Question 38

When cluster analysis is also used for clustering variables to identify homogeneous groups,the units used for analysis are the variables and the distance measures are computed for all pairs of variables.

Question 39

________ is a class of techniques used to classify objects or cases into relatively homogeneous groups.

A) Common factor analysis
B) Cluster analysis
C) Principal components analysis
D) Conjoint analysis

Question 40

A(n)________ or tree graph is a graphical device for displaying clustering results.Vertical lines represent clusters that are joined together.The position of the line on the scale indicates the distances at which clusters were joined.

A) scattergram
B) scree plot
C) icicle diagram
D) dendrogram

Question 41

________ is a clustering procedure characterized by the development of a tree-like structure.

A) Optimizing partitioning clustering
B) Non-hierarchical clustering
C) Hierarchical clustering
D) TwoStep clustering

Question 42

________ is a clustering procedure where each object starts out in a separate cluster.

A) Non-hierarchical clustering
B) Divisive clustering
C) Agglomerative clustering
D) Hierarchical clustering

Question 43

________ is a procedure that first assigns or determines a cluster center and then groups all objects within a pre-specified threshold value from the center.

A) Divisive clustering
B) Non-hierarchical clustering
C) Ward's method
D) Agglomerative clustering

Question 44

The ________ is a nonhierarchical method in which a cluster center is selected and all objects within a pre-specified threshold value from the center are grouped together.

A) Ward's procedure
B) optimizing partitioning method
C) sequential threshold method
D) parallel threshold method

Question 45

The ________ is a nonhierarchical method that allows for later reassignment of objects to clusters to optimize an overall criterion.

A) Ward's procedure
B) optimizing partitioning method
C) parallel threshold method
D) sequential threshold method

Question 46

________ is a variance method in which the squared euclidean distance to the cluster means is minimized.

A) Optimizing partitioning method
B) Parallel threshold method
C) Ward's procedure
D) Sequential threshold method

Question 47

The ________ method is based on minimum distance or the nearest neighbor rule.

A) medium linkage
B) complete linkage
C) average linkage
D) single linkage

Question 48

________ is a clustering procedure where all objects start out in one giant cluster.Clusters are formed by dividing this cluster into smaller and smaller clusters.

A) Divisive clustering
B) Agglomerative clustering
C) Hierarchical clustering
D) Non-hierarchical clustering

Question 49

Which of the following is not a disadvantage of nonhierarchical clustering procedures?

A) The number of clusters must be pre-specified.
B) The procedures do not work well when the clusters are poorly defined.
C) The selection of cluster centers is arbitrary.
D) All of the above are disadvantages.

Question 50

The most commonly used measure of similarity is the ________ or its square.

A) Chebychev's distance
B) Manhattan distance
C) euclidean distance
D) city-block distance

Question 51

Which cluster analysis procedure can automatically determine the optimal number of clusters by comparing the values of a model-choice across different clustering solutions?

A) Ward's method
B) divisive
C) TwoStep
D) sequential threshold

Question 52

________ is frequently referred to as k-means clustering.

A) Non-hierarchical clustering
B) Ward's method
C) Agglomerative clustering
D) Divisive clustering

Question 53

The ________ is a nonhierarchical method that specifies several cluster centers at once.All objects within a pre-specified threshold value from the center are grouped together.

A) optimizing partitioning method
B) Ward's procedure
C) parallel threshold method
D) sequential threshold method

Question 54

The ________ method uses information on all pairs of distances,not merely the minimum or maximum distances.

A) single linkage
B) average linkage
C) complete linkage
D) medium linkage

Question 55

Which of the following is a variance method of clustering?

A) optimizing partitioning
B) sequential threshold
C) complete linkage
D) Ward's method

Question 56

The ________ method is based on the maximum distance or the furthest neighbor approach.

A) medium linkage
B) single linkage
C) complete linkage
D) average linkage

Question 57

________ methods are commonly used in marketing research.

A) Agglomerative clustering
B) TwoStep clustering
C) Divisive clustering
D) Optimizing partitioning

Question 58

________ are agglomerative methods of hierarchical clustering in which clusters are generated to minimize the within-cluster variance.

A) Centroid methods
B) Variance methods
C) Parallel methods
D) Linkage methods

Question 59

Which of the methods below is not a hierarchical method?

A) parallel threshold
B) optimizing partitioning
C) both A and B
D) variance

Question 60

Which statement is not true concerning the clustering solution if the variables are measured in vastly different units?

A) We must standardize the data by rescaling each variable to have a mean of zero and standard deviation of unity.
B) Standardization can reduce the differences between groups on variables that may best discriminate groups or clusters.
C) It is desirable to eliminate outliers.
D) The clustering solution will not be influenced by the units of measurement.

Question 61

Which method allows the researcher to obtain information on cluster membership of cases if the number of clusters is specified?

A) cluster centers
B) scree plot
C) icicle plot
D) both A and C

Question 62

What suggested guidelines researchers can use when deciding on the number of clusters?

Question 63

If you are performing cluster analysis on the same data using different distance measures and then comparing the results across measures to determine stability of the solutions,you are at which stage of the cluster analysis process?

A) interpreting and profiling the clusters
B) deciding on the number of clusters
C) assessing reliability and validity
D) selecting a clustering procedure

Question 64

________ involves examining the cluster centroids.

A) Interpreting and profiling the clusters
B) Deciding on the number of clusters
C) Assessing reliability and validity
D) Selecting a clustering procedure

Question 65

To use cluster analysis for clustering variables to identify homogeneous groups,the researcher could do all of the following except ________.

A) inserting communalities in the diagonal of the correlation matrix
B) using the correlation coefficient as a measure of similarity between variables
C) using the variables as the units of analysis
D) A and B

Question 66

Which of the following is not a procedure to check the quality of clustering results?

A) Use the same method of clustering and compare the results.
B) Split the data randomly into halves.Perform clustering separately on each half.Compare cluster centroids across the two subsamples.
C) Perform cluster analysis on the same data using different distance measures.Compare the results across measures to determine the stability of the solutions.
D) Delete variables randomly.Perform clustering based on the reduced set of variables.Compare the results with those obtained by clustering based on the entire set of variables.

Question 67

What are the steps in conducting cluster analysis (Figure 20.3 in the text)?

Question 68

In SAS,the ________ program can be used for the hierarchical clustering of objects or cases.

A) CLUSTER ANALYSIS
B) FASTCLUS
C) HIERARCHICAL CLUSTER
D) VARCLUS

Question 69

In SPSS,the main program for hierarchical clustering of objects or cases is ________.

A) CLUSTER ANALYSIS
B) FASTCLUS
C) HIERARCHICAL CLUSTER
D) VARCLUS

Question 70

In non-hierarchical clustering,plotting the ratio of total within-group variance to between-group variance against the number of clusters is useful if you are ________.

A) interpreting and profiling the clusters
B) deciding on the number of clusters
C) assessing the validity of clustering
D) both B and C

Question 71

Which is best to use when selecting a clustering procedure: hierarchical or nonhierarchical clustering?

Question 72

Which method allows the researcher to obtain information on cluster membership of cases if the number of clusters is specified?

A) factor loading plot
B) scree plot
C) scattergram
D) icicle plot

Question 73

Why should the clustering of variables be used?