Block 14
Objective 5: How to select the appropriate measure of association
We have just covered quite a
bit of information–information about a confounding array of nominal and
ordinallevel measures of association. As a result of this inundation of
information, you may still be confused about the appropriate measure to use.
Remember we said that selection depends on the level of measurement, the size of
the table, and whether you hypothesize a direction in a relationship, or specify
causality. Confusing, right? The purpose of Table 1411 is to alleviate some of
your confusion by giving you help in selecting the appropriate measure of
association.
Table 1411. Choosing the Appropriate Measure of Association 
Measure of Association 
Table Size 
Asymmetrical/ Symmetrical 
General Comments 
Nominal Measures 



Phi coefficient 
2
by 2 
Symmetrical 
Limited by the size of the table. 
Cramer's V 
Any size 
Symmetrical 
Preferable to C. Because it can attain a value of
1.0. 
Contingency coefficient (C) 
Larger tables 
Symmetrical 
Upper limit is somewhat less than 1.0. 
Lambda 
Any size 
Asymmetrical 
PRE measure. Can underestimate the degree of the
relationship. 
Ordinal Measures 



Gamma 
Any size 
Symmetrical 
PRE measure. Can overestimate the degree of
relationship. 
Tau b 
Square tables 
Symmetrical 
PRE measure. Limited by shape of table. 
Tau c 
Any size 
Symmetrical 
PRE measure. More useful than tau b. 
Sommer's D 
Any size 
Asymmetrical 
PRE measure. Use when you know the direction of the
relationship. 

