APPENDIX A

SAS Syntax

/* Syntax for two-predictor Poisson regression */ 
proc genmod data = one; 
model y = gender sensation/dist = poisson link = log; 
output out = plots poi predicted = pred count resdev = dev resid
stdresdev = stud dev resid leverage = hat diagonal cooksd = all dfbetas = all ; 
run; 

/* Syntax for Figure 4 */
symbol1 color = black value = x interpol = sm50s; 
proc gplot data = plots poi; 
plot dev resid * pred count; 
title2 “Deviance residuals vs predicted count for two-predictor Poisson model”;
run; 

/* Syntax for index plot of leverage */ 
symbol1 color = black value = x; 
proc gplot data = plots poi; 
plot hat diagonal * case;
title2 “Index plot of leverage statistics (Hat diagonal) for all cases”; 
run; 

/* Syntax for two-predictor overdispersed Poisson regression */ 
proc genmod data = one;
model y = gender sensation/dist = poisson link = log scale = d; 
output out = plots odpoi predicted = pred count resdev = dev resid;
run; 

/* Syntax for two-predictor negative binomial regression */ 
proc genmod data = one; 
model y = gender sensation/dist = nb link = log; 
output out = plots nb predicted = pred count resdev = dev resid; 
run; 

/* Syntax for two-predictor negative binomial regression, testing for overdispersion */ 
proc genmod data = one; 
model y = gender sensation/dist = nb link = log noscale; 
output out = plots nb test predicted = pred count resdev = dev resid; 
run;