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Multidimensional Scaling by zhangyun

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									  Multidimensional Scaling
Multidimensional scaling (MDS) can be considered
to be an alternative to factor analysis. In general,
the goal of the analysis is to detect meaningful
underlying dimensions that allow the researcher
to explain observed similarities or dissimilarities
(distances) between the investigated objects. In
factor analysis, the similarities between objects
(e.g., variables) are expressed in the correlation
matrix. With MDS one may analyse any kind of
similarity or dissimilarity matrix, in addition to
correlation matrices.
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  Multidimensional Scaling
The data are from an experiment in which
subjects were asked to look at a screen, which
had two circular opaque glass windows. These
windows were lit from two projectors behind the
screen. Different colour filters could be inserted
in the projectors. Fourteen colour filters were
used. Each stimulus was combined with each other
stimulus in a random order. The subjects were
then asked to rate the degree of “qualitative
similarity” between each pair of colour filters on a
5-point scale. The similarity matrix is provided.
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     Multidimensional Scaling
Analyze > Scale > Multidimensional Scaling (PROXSCAL)




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     Multidimensional Scaling
A single matrix of proximities has been provided.




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     Multidimensional Scaling
Choose define and select all proximities.




                                            5
     Multidimensional Scaling
Choose model, ordinal similarities.




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     Multidimensional Scaling
Choose Torgerson as an initial configuration in options




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     Multidimensional Scaling
The first analysis may now be performed.




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     Multidimensional Scaling
Strictly you should employ numerous random restarts to
ensure a true minimum has been located.

The current solution suggests that only one dimension
should suffice.




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     Multidimensional Scaling
Restrict the model to one dimension.




                                       10
     Multidimensional Scaling
Restrict the model to one dimension.




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