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Directional measures quantify the reduction in the error of predicting
the row variable value when you know the column variable value, or vice versa. Each measure simply has a different definition of "error."
Lambda defines
error as the misclassification of cases, and cases are
classified according to the modal (most frequent)
category.
Tau defines
error as the misclassification of a case, and cases are
classified into category
j with probability equal to the
observed frequency of category j.
The uncertainty
coefficient defines error as the entropy,
or P(category j) *
ln(P(category j))
summed over the categories of the variable.
The uncertainty coefficient
is also known as Theil's U.
For customers who had contact, the Goodman and Kruskal's tau value of 0.031 with
Store dependent means that there is a 3.1% reduction in
misclassification.
The other measures report equally small values, indicating
that the association between Store and
Service satisfaction is almost solely due to the poor service
at store 2.
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Directional Measures |