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Inter-relationships between variables

3.3 Spurious correlation

 Correlation does not necessarily imply causality, especially if a third factor is
involved.

3.4 Spearman’s rank correlation = R

 Looks at the link between the ranking of a set of objects and one of their
properties

 For example, to what extent would customer perceived quality (ranking)
correlate with the price (property) of a product?

6∑d 2
 R = 1 -
2
n(n –1)

 The interpretation of R-values (and warnings!) is similar to that for r.

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