I know it's odd. Here is my codes. I'm assuming when I define NB distribution it should give me overdispersion. data crash; input Intersection y major minor accident Wt; datalines; 1 3 9.8 9.9 10 0 1 4 9.7 9.8 10 0 1 5 9.8 9.8 9 0 1 6 9.9 9.8 4 -1.10 2 2 10.7 9.5 38 0 2 3 10.7 9.5 46 0 2 4 10.7 9.6 44 0 2 5 10.7 39 -0.29 3 1 11.0 9.2 41 0 3 2 11.0 9.3 49 0 3 3 11.1 9.3 40 0 3 4 11.1 9.4 20 -1.10 4 2 10.4 10.0 40 0 4 3 10.4 10.1 31 0 4 4 10.2 9.9 45 0 4 5 10.3 10.1 38 -0.29 5 3 10.6 10.4 78 0 5 4 10.6 10.4 64 0 5 5 10.6 10.4 54 0 5 6 10.6 27 -1.39 6 2 10.4 10.1 57 0 6 3 10.4 10.1 51 0 6 4 10.2 10.1 49 0 6 5 10.3 10.2 14 -1.39 7 2 10.5 10.4 56 0 7 3 10.5 10.4 41 0 7 4 10.4 10.4 50 0 7 5 10.6 10.4 21 -0.54 8 2 10.3 9.6 41 0 8 3 10.3 9.7 31 0 8 4 10.4 9.7 33 0 8 5 10.4 9.9 9 -1.39 9 1 10.2 8.7 20 0 9 2 10.1 8.6 4 0 9 3 10.2 8.5 14 0 9 4 10.0 8.2 15 0 9 5 10.1 8.6 8 0 9 6 10.1 8.6 11 0 10 1 9.9 8.0 13 0 10 2 9.9 8.0 9 0 10 3 10.0 8.1 12 0 10 4 10.1 8.1 10 0 10 5 10.1 8.2 12 0 10 6 10.0 8.1 16 0 ; run; proc genmod data=crash; class Intersection y; model accident = major minor/ dist=nb link=log offset= Wt type3 wald; Repeated Subject=Intersection; run; quit; ... View more

and this is how I did that: data crash; input major minor accident; datalines; 9.8 9.9 10 9.7 9.8 10 9.8 9.8 9 10.7 9.5 38 10.7 9.5 46 10.7 9.6 44 11.0 9.2 41 11.0 9.3 49 11.1 9.3 40 10.4 10.0 40 10.4 10.1 31 10.2 9.9 45 10.6 10.4 78 10.6 10.4 64 10.6 10.4 54 10.4 10.1 57 10.4 10.1 51 10.2 10.1 49 10.5 10.4 56 10.5 10.4 41 10.4 10.4 50 10.3 9.6 41 10.3 9.7 31 10.4 9.7 33 ; run; ods graphic on; proc genmod data=crash; model accident = major minor / dist=negbin link=log; assess link / crpanel; run; ods graphics off; I can see a "panel of cumulative Sum Residual Plot" but it's blank and doesn't show any plot. ... View more

There is also another problem, I used the following to see the fitted model graph ods graphic on; proc genmod data=crash; model accident = major minor / dist=negbin link=log; assess link / resample=10000 seed=603708000 crpanel; run; ods graphics off; but it doesn't shoe anything in panel of cumulative sum residual plot. Do I need to modify anything? Thanks. ... View more

Is there anyway in genmod procedure with NB dist that you can get a different parameter "α" beside the main parameters and overdispersion? ... View more

so Log link is actually natural log or ln. is that correct? ... View more

I think this is what you mean: Analysis Of Maximum Likelihood Parameter Estimates Standard Wald 95% Confidence Wald Parameter DF Estimate Error Limits Chi-Square Pr > ChiSq Intercept 1 1.8966 0.3498 1.2111 2.5822 29.40 <.0001 major1 1 0.0271 0.0063 0.0147 0.0395 18.32 <.0001 minor1 1 0.0378 0.0075 0.0232 0.0524 25.79 <.0001 Dispersion 1 0.0610 0.0277 0.0251 0.1484 NOTE: The negative binomial dispersion parameter was estimated by maximum likelihood. this shows the estimated parameters for each variable. my question is that what is the functional form. Is it like accident= 0.0271(major1)+0.0378(minor1)+1.8966 or is there any option that shows how do they relate? thanks ... View more

what is the mathematical relationship between accident as dependent variable and major and minor as explanatory variables? ... View more

One more question. in proc genmod, is there anyway I can see the functional form of the regression model. For this example how these variables are related? Thanks ... View more

I've been struggling with this for awhile and now it works. I really appreciate it:) ... View more