Posted by
Bob Schacht-3 on
Sep 20, 2006; 8:11pm
URL: http://spssx-discussion.165.s1.nabble.com/Association-between-two-nominal-variables-tp1071026p1071033.html
At 04:42 AM 9/20/2006, Secrist, Kevin wrote:
>Thank you Bob and everyone who responded to my question.
>
>I utilized phi and Cramer's V. and got an value of -.128 for phi and .128
>for Cramer's V. So, as I understand it, the association between my
>variable and outcome is rather low. Is there an interpretive scale of
>influence like correlation coefficient
>.0 to .2 weak or no relationship
>.2 to .4 weak relationship
>.4 to .6 moderate relationship
>.6 to .8 strong relationship
>.8 to 1.0 very strong relationship
>(Salkind, Neil "Statistics for People who think they hate statistics, 2000
>pg. 96)
Kevin,
The Phi coefficient is related to the Chi-Square statistic; Blalock* says
Phi-square = Chi-square/N.
So I guess you could calculate N*Phi(squared) and use the Chi-square
tables. Of course, you could also just calculate the Chi-square directly.
Why are you avoiding the use of a simple Chi-square?
BTW, for a 2x2 table you should probably be using Fisher's exact test
anyway. Why not?
Bob
*Blalock, Hubert M. (rev. ed., 1972) Social Statistics.
Yes, there are more recent editions, but they weren't in print yet when I
was in grad school <g>
>-----Original Message-----
>From: SPSSX(r) Discussion [mailto:
[hidden email]]On Behalf Of
>Bob Schacht
>Sent: Tuesday, September 19, 2006 4:32 PM
>To:
[hidden email]
>Subject: Re: Association between two nominal variables?
>
>
>At 12:42 PM 9/19/2006, Dominic Lusinchi wrote:
> >Kevin,
> >
> >For a 2X2 table you can use the Phi statistic, available in the Crosstab
> >procedure under Statistics. Phi varies from 0 to 1: closer to 1, stronger
> >the association. Of course this assumes that the chi-square statistic is
> >significant. . .
>
>Of interest in this choice is whether the double null category is
>meaningful-- that is, if Peer Pal is "no" (0) and the outcome labeled outpt
>(for outpatient service received) is also no (0). If the double null is
>meaningful and not merely a default, then the strength of Phi may depend
>largely on how many double nulls there are. Is your sample population
>defined in such a way that the double null applies to them differently than
>to the 3 billion other people in the world for whom these two variables
>have a value of 0?
>
>If the double nulls are a poorly defined category, then you might want to
>consider Jaccard's coefficient, which does not use the double nulls
>(
http://en.wikipedia.org/wiki/Jaccard_index). It is extremely easy to
>calculate.
>
>Bob
>
>
>
>
>Robert M. Schacht, Ph.D. <
[hidden email]>
>Pacific Basin Rehabilitation Research & Training Center
>1268 Young Street, Suite #204
>Research Center, University of Hawaii
>Honolulu, HI 96814