Re: Percent Change Crosstabs

Posted by Bruce Weaver on May 29, 2013; 9:21pm
URL: http://spssx-discussion.165.s1.nabble.com/Percent-Change-Crosstabs-tp5720440p5720474.html

Thanks Tony, I didn't know that.  Here's a demo using the OP's data.  

DATA LIST list / Group Recid kount (3f5.0).
BEGIN DATA
1 1 816
1 2 1133
2 1 936
2 2 1013
END DATA.

WEIGHT by kount.

* Get the risk difference via GENLIN first.

GENLIN Recid BY Group
   /MODEL Group INTERCEPT=YES
  DISTRIBUTION=NORMAL LINK=IDENTITY
   /CRITERIA SCALE=MLE COVB=ROBUST PCONVERGE=1E-006(ABSOLUTE) SINGULAR=1E-012
 ANALYSISTYPE=3(LR)
     CILEVEL=95 CITYPE=WALD LIKELIHOOD=FULL
   /MISSING CLASSMISSING=EXCLUDE
   /PRINT CPS DESCRIPTIVES MODELINFO FIT SUMMARY SOLUTION.

* Now use CROSSTABS, with RISK and Somer's D reported.

CROSSTABS
  /TABLES=Group BY Recid
  /FORMAT=AVALUE TABLES
  /STATISTICS=D RISK
  /CELLS=COUNT ROW
  /COUNT ROUND CELL.

RESULTS

Genlin: B = .062, SE = .0159, 95% CI, .030 to .093

CROSSTABS gives the following values for d and its SE:
   d     SE
-.062 .0160 -- Symmetric
-.062 .0161 -- Group Dependent
-.062 .0159 -- Recid Dependent

So, the Recid Dependent result is the one that matches what I got from GENLIN.  (The difference in sign could be fixed by changing the reference category in one of the analyses.)  

Once again, though, I prefer the GENLIN solution, because I don't have to know which of 3 results to choose, and I get a CI for the risk difference (which is not given for Somer's d).

Anthony Babinec wrote

In the 2x2 table, the measure Somers' d equals the difference in
proportions.
You have to choose the right Somers' d, since Crosstabs prints several
calculated
versions, but you do get accompanying standard errors and significance
levels.


Tony Babinec
[hidden email]

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