User Guide

332
Chapter 16
Ordinal. For tables in which both rows and columns contain ordered values, select
Gamma (zero-order for 2-way tables and conditional for 3-way to 10-way tables),
Kendall’s t
au-b
,andKendall’s tau-c. For predicting column categories from row
categories, select Somers’ d.
 Gamma. A symmetric measure of association between two ordinal variables that
ranges betw
een -1 and 1. Values close to an absolute value of 1 indicate a strong
relationship between the two variables. Values close to zero indicate little or no
relationship. For 2-way tables, zero-order gammas are displayed. For 3-way to
n-way tabl
es, conditional gammas are displayed.
 Somers' d
.
A measure of association between two ordinal variables that ranges
from -1 to 1. Values close to an absolute value of 1 indicate a strong relationship
between the two variables, and values close to 0 indicate little or no relationship
between t
he variables. Somers' d is an asymmetric extension of gamma that
differs only in the inclusion of the number of pairs not tied on the independent
variable. A symmetric version of this statistic is also calculated.
 Kendall's tau-b. A nonparametric measure of correlation for ordinal or ranked
variable
s that take ties into account. The sign of the coefficient indicates the
direction of the relationship, and its absolute value indicates the strength, with
larger absolute values indicating stronger relationships. Possible values range
from -1 t
o 1, but a value of -1 or +1 can only be obtained from square tables.
 Kendal
l's tau-c.
A nonparametric measure of association for ordinal variables that
ignores ties. The sign of the coefficient indicates the direction of the relationship,
and its absolute value indicates the strength, with larger absolute values indicating
strong
er relationships. Possible values range from -1 to 1, but a value of -1 or +1
can only be obtained from square tables.
Nominal by Interval. When one variable is categorical and the other is quantitative,
select
Eta. The categorical variable must be coded numerically.
 Eta. A
measure of association that ranges from 0 to 1, with 0 indicating no
association between the row and column variables and values close to 1
indicating a high degree of association. Eta is appropriate for a dependent
varia
ble measured on an interval scale (for example, income) and an independent
variable with a limited number of categories (for example, gender). Two eta
values are computed: one treats the row variable as the interval variable; the other
treat
s the column variable as the interval variable.