Examples

Cytel's LogXact 5 vs. SAS's PROC LOGISTIC:
Antibiotics and Diarrhea in Hospitalized Patients

(Source: From data gathered at the Cornell Medical Center by Jaffe and Chang, 1993.)

Data on 2493 hospitalized patients were gathered to determine the relationship between antibiotic use and an acute form of diarrhea -- clostridium dificile-induced diarrhea (DIARRHED).
(2493 observations, 10 covariates.)

The results are presented below. Note that SAS fails to fit the logistic regression model -- only LogXact 5 can do it.

LOGXACT 5 RESULTS

=============================================================================================
Parameter Estimates
=============================================================================================
                   Point Estimate            Confidence interval and P-value for Beta
         Type  Beta        SE(Beta)    Type        95.0%     C.I.            Pvalue      SE      
                                                   Lower       Upper       2*1-sided   
=============================================================================================
aged      MLE  ?           ?           Asymptotic  ?           ?           ?                   
bactrppod MLE  ?           ?           Asymptotic  ?           ?           ?                   
cdifprod  MLE  ?           ?           Asymptotic  ?           ?           ?                   
cephalxd  MLE  ?           ?           Asymptotic  ?           ?           ?                   
clindamd  MLE  ?           ?           Asymptotic  ?           ?           ?                   
gentaivd  MLE  ?           ?           Asymptotic  ?           ?           ?                   
losd      MLE  ?           ?           Asymptotic  ?           ?           ?                   

scuoccud  MLE  ?           ?           Asymptotic  ?           ?           ? 
          CMLE 0.6549      0.3011      Monte Carlo 0.0048      1.2822      0.0462      0.0030    
                                       ( Seed=1035244198,Samples=10000 )

sexd      MLE  ?           ?           Asymptotic  ?           ?           ?                   
tgcephd   MLE  ?           ?           Asymptotic  ?           ?           ?                   
%CONST    MLE  ?           ?           Asymptotic  ?           ?           ?                   
=============================================================================================

Analysis time: 00:11:35
=============================================================================================
SAS's PROC LOGISTIC RESULTS
WARNING: There is not enough memory available for exact computations.

Try it yourself!
The links below include data files and SAS code that you can download.

LOGXACT 5--
Download LogXact data
View Instructions for LogXact 5 analysis

PROC LOGISTIC--
Download SAS code (includes data)