SPSS Step-by-Step Tutorial and Statistical Guides by Statswork
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This document provides an overview of cluster analysis techniques used in marketing research. It defines cluster analysis as classifying cases into homogeneous groups based on a set of variables. Cluster analysis can be used for market segmentation, understanding buyer behaviors, and identifying new product opportunities in marketing research. The document outlines the steps to conduct cluster analysis, including selecting a distance measure and clustering algorithm, determining the number of clusters, and validating the analysis. It provides examples of hierarchical and non-hierarchical clustering methods like k-means and discusses choosing between these approaches. SPSS is used to demonstrate a cluster analysis example analyzing supermarket customer data.
SPSS Step-by-Step Tutorial and Statistical Guides by Statswork
- 1. SPSS Tutorial AEB 37 / AE 802 Marketing Research Methods Week 7
- 2. Cluster Analysis Lecture / Tutorial outline • Cluster analysis • Example of cluster analysis • Work on the assignment
- 3. Cluster Analysis-Contid… • It is a class of techniques used to classify cases into groups that are relatively homogeneous within themselves and heterogeneous between each other, on the basis of a defined set of variables. These groups are called clusters.
- 4. Cluster Analysis and marketing research • Market segmentation. E.g. clustering of consumers according to their attribute preferences • Understanding buyers behaviours. Consumers with similar behaviours/characteristics are clustered • Identifying new product opportunities. Clusters of similar brands/products can help identifying competitors / market opportunities • Reducing data. E.g. in preference mapping
- 5. Steps to conduct a Cluster Analysis 1. Select a distance measure 2. Select a clustering algorithm 3. Determine the number of clusters 4. Validate the analysis
- 6. REGR factor score 2 for analysis 1 43210-1-2-3 3 2 1 0 -1 -2 -3 -4 • Steps to conduct a Cluster Analysis - Contd
- 7. Defining distance: the Euclidean distance 2 1 n ij ki kj k D x x Dij distance between cases i and j xki value of variable Xk for case j Problems: • Different measures = different weights • Correlation between variables (double counting) Solution: Principal component analysis
- 8. Clustering procedures • Hierarchical procedures – Agglomerative (start from n clusters, to get to 1 cluster) – Divisive (start from 1 cluster, to get to n cluster) • Non hierarchical procedures – K-means clustering
- 10. Agglomerative clustering • Linkage methods – Single linkage (minimum distance) – Complete linkage (maximum distance) – Average linkage • Ward’s method 1. Compute sum of squared distances within clusters 2. Aggregate clusters with the minimum increase in the overall sum of squares • Centroid method – The distance between two clusters is defined as the difference between the centroids (cluster averages)
- 11. K-means clustering 1. The number k of cluster is fixed 2. An initial set of k “seeds” (aggregation centres) is provided • First k elements • Other seeds 3. Given a certain treshold, all units are assigned to the nearest cluster seed 4. New seeds are computed 5. Go back to step 3 until no reclassification is necessary Units can be reassigned in successive steps (optimising partioning)
- 12. Hierarchical vs Non hierarchical methods Hierarchical clustering • No decision about the number of clusters • Problems when data contain a high level of error • Can be very slow • Initial decision are more influential (one-step only) Non hierarchical clustering • Faster, more reliable • Need to specify the number of clusters (arbitrary) • Need to set the initial seeds (arbitrary)
- 13. Suggested approach 1. First perform a hierarchical method to define the number of clusters 2. Then use the k-means procedure to actually form the clusters
- 14. Defining the number of clusters: elbow rule (1) Agglomeration Schedule 4 7 .015 0 0 4 6 10 .708 0 0 5 8 9 .974 0 0 4 4 8 1.042 1 3 6 1 6 1.100 0 2 7 4 5 3.680 4 0 7 1 4 3.492 5 6 8 1 11 6.744 7 0 9 1 2 8.276 8 0 10 1 12 8.787 9 0 11 1 3 11.403 10 0 0 Stage 1 2 3 4 5 6 7 8 9 10 11 Cluster 1 Cluster 2 Cluster Combined Coefficients Cluster 1 Cluster 2 Stage Cluster First Appears Next Stage Stage Number of clusters 0 12 1 11 2 10 3 9 4 8 5 7 6 6 7 5 8 4 9 3 10 2 11 1 n
- 15. Elbow rule (2): the scree diagram 0 2 4 6 8 10 12 11 10 9 8 7 6 5 4 3 2 1 Number of clusters Distance
- 16. Validating the analysis • Impact of initial seeds / order of cases • Impact of the selected method • Consider the relevance of the chosen set of variables
- 17. SPSS Example
- 19. Agglomeration Schedule 3 6 .026 0 0 8 2 5 .078 0 0 7 4 9 .224 0 0 5 1 7 .409 0 0 6 4 10 .849 3 0 8 1 8 1.456 4 0 7 1 2 4.503 6 2 9 3 4 9.878 1 5 9 1 3 18.000 7 8 0 Stage 1 2 3 4 5 6 7 8 9 Cluster 1 Cluster 2 Cluster Combined Coefficients Cluster 1 Cluster 2 Stage Cluster First Appears Next Stage Number of clusters: 10 – 6 = 4 SPSS Example
- 20. Component1 2.01.51.0.50.0-.5-1.0-1.5 Component2 1.5 1.0 .5 0.0 -.5 -1.0 -1.5 -2.0 Cluster Number of Ca 4 3 2 1 LUCY JULIA FRED ARTHUR JENNIFER THOMAS MATTHEW NICOLE PAMELA JOHN SPSS Example
- 21. Open the dataset supermarkets.sav From your N: directory (if you saved it there last time Or download it from: http://www.rdg.ac.uk/~aes02mm/supermarket.sav • Open it in SPSS
- 23. Run Principal Components Analysis and save scores • Select the variables to perform the analysis • Set the rule to extract principal components • Give instruction to save the principal components as new variables
- 24. Cluster analysis: basic steps • Apply Ward’s methods on the principal components score • Check the agglomeration schedule • Decide the number of clusters • Apply the k-means method
- 26. Select the component scores Select from here Untick this
- 29. Number of clusters Identify the step where the “distance coefficients” makes a bigger jump
- 30. The scree diagram (Excel needed) Distance 0 100 200 300 400 500 600 700 800 118 120 122 124 126 128 130 132 134 136 138 140 142 144 146 148 Step
- 31. Number of clusters Number of cases 150 Step of ‘elbow’ 144 __________________________________ Number of clusters 6
- 32. Now repeat the analysis • Choose the k-means technique • Set 6 as the number of clusters • Save cluster number for each case • Run the analysis
- 33. K-means
- 34. K-means dialog box Specify number of clusters
- 35. Save cluster membership Click here first Thick here
- 36. Final output
- 38. Component meaning (tutorial week 5) Component Matrixa .810 -.294 -4.26E-02 .183 .173 .480 -.152 .347 .334 -5.95E-02 .525 -.206 -.475 -4.35E-02 .140 .192 -.345 -.127 .383 .199 .646 -.281 -.134 -.239 -.207 .536 .619 -.102 -.172 6.008E-02 .492 -.186 .190 .460 .342 1.784E-02 -9.24E-02 .647 -.287 .507 .649 .612 .135 -6.12E-02 -3.29E-03 .369 .663 .247 .184 1.694E-02 .124 -9.53E-02 .462 .232 -.529 2.989E-02 .406 -.349 .559 -8.14E-02 .443 -.271 .182 -5.61E-02 -.465 .908 -4.75E-02 -7.46E-02 -.197 -3.26E-02 .891 -5.64E-02 -6.73E-02 -.228 6.942E-04 Monthly amount spent Meat expenditure Fish expenditure Vegetables expenditure % spent in own-brand product Own a car % spent in organic food Vegetarian Household Size Number of kids Weekly TV watching (hours) Weekly Radio listening (hours) Surf the web Yearly household income Age of respondent 1 2 3 4 5 Component Extraction Method: Principal Component Analysis. 5 components extracted.a. 1. “Old Rich Big Spender” 3. Vegetarian TV lover 4. Organic radio listener 2. Family shopper 5. Vegetarian TV and web hater
- 39. Final Cluster Centers -1.34392 .21758 .13646 .77126 .40776 .72711 .38724 -.57755 -1.12759 .84536 .57109 -.58943 -.22215 -.09743 1.41343 .17812 1.05295 -1.39335 .15052 -.28837 -.30786 1.09055 -1.34106 .04972 .04886 -.93375 1.23631 -.11108 .31902 .87815 REGR factor score 1 for analysis 1 REGR factor score 2 for analysis 1 REGR factor score 3 for analysis 1 REGR factor score 4 for analysis 1 REGR factor score 5 for analysis 1 1 2 3 4 5 6 Cluster Component meaning (tutorial week 5)
- 40. Cluster interpretation through mean component values • Cluster 1 is very far from profile 1 (-1.34) and more similar to profile 2 (0.38) • Cluster 2 is very far from profile 5 (-0.93) and not particularly similar to any profile • Cluster 3 is extremely similar to profiles 3 and 5 and very far from profile 2 • Cluster 4 is similar to profiles 2 and 4 • Cluster 5 is very similar to profile 3 and very far from profile 4 • Cluster 6 is very similar to profile 5 and very far from profile 3
- 41. Which cluster to target? • Objective: target the organic consumer • Which is the cluster that looks more “organic”? • Compute the descriptive statistics on the original variables for that cluster
- 42. Representation of factors 1 and 4 (and cluster membership) REGR factor score 1 for analysis 1 210-1-2-3 3 2 1 0 -1 -2 -3 Cluster Number of Ca 6 5 4 3 2 1
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