WARNING: The relative Hessian convergence criterion of 806.74 is greater than the limit of 0.0001.

[palolix]

Dear SAS Community,

I am running a negbin model in genmod to compare days to ripe (DTR), a discrete response variable, between avocado varieties. I choose a negbin dist since the variance (10.17) exceeds the mean (6.31). This is how the data looks like 

This is the code I'm using but I'm getting this warning:

 WARNING: The relative Hessian convergence criterion of 806.74527257 is greater than the limit of 0.0001. The
convergence is questionable.

proc genmod data=one;
class Harvest Variety Wks;
model DTR=Harvest|Variety|Wks/type3 dist=negbin link= log;
slice Harvest*Variety*Wks/sliceby=Harvest*Wks diff adjust=simulate(seed=1);
run;

Harvest (harvest month), and Wks (weeks) are categorical indep variables. I want to compare the DTR between varieties at each Week for each Harvest.

I would greatly appreciate if you could help me with this warning.

Thank you very much!

[StatDave]

You didn't show the results of the model fit, particularly the goodness of fit table and the parameter estimates table showing the model parameter estimates including the negative binomial dispersion parameter. One possible reason for the warning, though certainly not the only one, is if the dispersion parameter is essentially zero which means that the distribution is really Poisson. You can test if there is significant overdispersion as can be caused by extra variability by rerunning your GENMOD step and adding the SCALE=0 NOSCALE options in the MODEL statement as discussed in this note. If the test is not significant, then consider using the Poisson distribution. Another possible problem is that the complexity of the model makes estimating all the parameters difficult. You could try fitting simpler models such as by eliminating some of the interaction terms. In fact you can use a model selection method, such as the Lasso method, by using the HPGENSELECT to find an adequate but simpler model.

[palolix]

Thank you so much for your help StatDave!

I rerun the model adding the scale=0 statement:

proc genmod data=one;
class Harvest Variety Wks;
model DTR=Harvest|Variety|Wks/type3 dist=negbin link=log scale=0 noscale;
slice Harvest*Variety*Wks/sliceby=Harvest*Wks diff adjust=simulate(seed=1);
run;

The overdispersion was significant. Now I do not get the warning, so I guess I will use this model using negbin and the scale statement. This is what I get in the Log window:

Algorithm converged.
NOTE: The negative binomial dispersion parameter was held fixed.

Lagrange Multiplier Statistics
Parameter	Chi-Square	Pr > ChiSq
Dispersion	5766.4406	<.0001	*
* One-sided p-value

Fit table after rerunning the model:

Criteria For Assessing Goodness Of Fit
Criterion	DF	Value	Value/DF
Deviance	6018	2669.0119	0.4435
Scaled Deviance	6018	2669.0119	0.4435
Pearson Chi-Square	6018	2651.8346	0.4407
Scaled Pearson X2	6018	2651.8346	0.4407
Log Likelihood		36356.2831
Full Log Likelihood		-12484.2748
AIC (smaller is better)		25364.5496
AICC (smaller is better)		25377.6465
BIC (smaller is better)		26698.0562

Fit table and Parameter Estimates from previous model: 

Criteria For Assessing Goodness Of Fit
Criterion	DF	Value	Value/DF
Deviance	6018	2669.0119	0.4435
Scaled Deviance	6018	2669.0119	0.4435
Pearson Chi-Square	6018	2651.8176	0.4406
Scaled Pearson X2	6018	2651.8176	0.4406
Log Likelihood		36356.2831
Full Log Likelihood		-12484.2748
AIC (smaller is better)		25366.5496
AICC (smaller is better)		25379.7810
BIC (smaller is better)		26706.7911

WARNING: The relative Hessian convergence criterion of 0.0007461174 is greater than the limit of 0.0001. The convergence is questionable

Analysis Of Maximum Likelihood Parameter Estimates
Parameter				DF	Estimate	Standard Error	Wald 95% Confidence Limits		Wald Chi-Square	Pr > ChiSq
Intercept				1	2.0541	0.0801	1.8972	2.2110	658.23	<.0001
Harvest	1			1	-0.5014	0.1003	-0.6980	-0.3049	24.99	<.0001
Harvest	2			1	-0.3817	0.1054	-0.5883	-0.1752	13.12	0.0003
Harvest	3			1	-1.0156	0.1235	-1.2577	-0.7735	67.59	<.0001
Harvest	4			1	-0.8832	0.1190	-1.1164	-0.6499	55.08	<.0001
Harvest	5			1	-1.0033	0.1158	-1.2302	-0.7764	75.10	<.0001
Harvest	6			1	-0.7743	0.1084	-0.9868	-0.5617	50.98	<.0001
Harvest	8			1	-0.7368	0.1043	-0.9412	-0.5324	49.92	<.0001
Harvest	10			1	-0.3314	0.1239	-0.5741	-0.0886	7.16	0.0075
Harvest	11			1	-0.2963	0.1035	-0.4992	-0.0933	8.19	0.0042
Harvest	12			0	0.0000	0.0000	0.0000	0.0000	.	.
Variety	464918_99			1	-0.0064	0.1134	-0.2287	0.2158	0.00	0.9548
Variety	465418_99			1	-0.1335	0.0978	-0.3252	0.0582	1.86	0.1722
Variety	465502_99			1	0.0564	0.1309	-0.2001	0.3129	0.19	0.6664
Variety	465518_99			1	-0.0129	0.1136	-0.2355	0.2097	0.01	0.9096
Variety	467352_00			1	0.2921	0.1334	0.0307	0.5536	4.80	0.0285
Variety	BL516			1	0.0574	0.0914	-0.1218	0.2365	0.39	0.5301
Variety	EarlyGreen			1	-0.6678	0.1375	-0.9374	-0.3983	23.58	<.0001
Variety	Eugenin			1	-0.1520	0.1178	-0.3829	0.0788	1.67	0.1968
Variety	Flavia			1	-0.1595	0.1180	-0.3908	0.0718	1.83	0.1765
Variety	GEM			1	0.1471	0.1012	-0.0513	0.3455	2.11	0.1461
Variety	Hass			0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	1	464918_99		1	0.2202	0.1442	-0.0624	0.5028	2.33	0.1267
Harvest*Variety	1	465418_99		1	0.2672	0.1499	-0.0266	0.5611	3.18	0.0746
Harvest*Variety	1	465518_99		1	0.3373	0.1385	0.0658	0.6088	5.93	0.0149
Harvest*Variety	1	BL516		1	0.2617	0.1207	0.0252	0.4983	4.70	0.0301
Harvest*Variety	1	EarlyGreen		1	-0.1917	0.2244	-0.6314	0.2480	0.73	0.3928
Harvest*Variety	1	Eugenin		1	0.3911	0.1608	0.0759	0.7062	5.92	0.0150
Harvest*Variety	1	Flavia		1	0.3986	0.1610	0.0831	0.7141	6.13	0.0133
Harvest*Variety	1	GEM		1	-0.0706	0.1539	-0.3723	0.2312	0.21	0.6467
Harvest*Variety	1	Hass		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	2	464918_99		1	0.1341	0.1473	-0.1546	0.4227	0.83	0.3626
Harvest*Variety	2	465418_99		1	0.0349	0.1394	-0.2384	0.3082	0.06	0.8022
Harvest*Variety	2	465518_99		1	0.0543	0.1487	-0.2371	0.3457	0.13	0.7150
Harvest*Variety	2	BL516		1	0.0281	0.1472	-0.2605	0.3166	0.04	0.8488
Harvest*Variety	2	Eugenin		1	0.2797	0.1638	-0.0414	0.6007	2.91	0.0878
Harvest*Variety	2	Flavia		1	0.2363	0.1653	-0.0877	0.5603	2.04	0.1528
Harvest*Variety	2	Hass		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	3	464918_99		1	0.0993	0.1945	-0.2819	0.4806	0.26	0.6096
Harvest*Variety	3	465418_99		1	0.4431	0.1772	0.0958	0.7904	6.25	0.0124
Harvest*Variety	3	465518_99		1	0.4388	0.1659	0.1136	0.7640	6.99	0.0082
Harvest*Variety	3	BL516		1	-0.1404	0.1909	-0.5145	0.2337	0.54	0.4621
Harvest*Variety	3	Eugenin		1	-0.1446	0.2157	-0.5673	0.2782	0.45	0.5028
Harvest*Variety	3	Flavia		1	0.0571	0.2059	-0.3464	0.4606	0.08	0.7815
Harvest*Variety	3	GEM		1	0.3934	0.1715	0.0573	0.7294	5.26	0.0218
Harvest*Variety	3	Hass		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	4	465418_99		1	-0.2955	0.1709	-0.6305	0.0396	2.99	0.0839
Harvest*Variety	4	465518_99		1	-0.3036	0.2048	-0.7050	0.0977	2.20	0.1382
Harvest*Variety	4	467352_00		1	-0.5468	0.2560	-1.0486	-0.0450	4.56	0.0327
Harvest*Variety	4	BL516		1	0.1704	0.1493	-0.1222	0.4630	1.30	0.2536
Harvest*Variety	4	Eugenin		1	0.0797	0.2344	-0.3798	0.5392	0.12	0.7339
Harvest*Variety	4	Flavia		1	0.0533	0.2370	-0.4112	0.5178	0.05	0.8221
Harvest*Variety	4	GEM		1	0.1289	0.1545	-0.1740	0.4317	0.70	0.4043
Harvest*Variety	4	Hass		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	5	464918_99		1	-0.1083	0.1987	-0.4976	0.2811	0.30	0.5856
Harvest*Variety	5	465418_99		1	0.0382	0.1516	-0.2588	0.3353	0.06	0.8009
Harvest*Variety	5	467352_00		1	0.0433	0.1931	-0.3351	0.4218	0.05	0.8224
Harvest*Variety	5	BL516		1	0.8013	0.1509	0.5057	1.0970	28.22	<.0001
Harvest*Variety	5	Eugenin		1	-0.0879	0.2206	-0.5202	0.3444	0.16	0.6903
Harvest*Variety	5	Flavia		1	-0.0311	0.2437	-0.5087	0.4465	0.02	0.8984
Harvest*Variety	5	GEM		1	0.5068	0.1476	0.2175	0.7961	11.79	0.0006
Harvest*Variety	5	Hass		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	6	465418_99		1	-0.2990	0.1485	-0.5901	-0.0080	4.05	0.0441
Harvest*Variety	6	467352_00		1	-0.4734	0.2130	-0.8909	-0.0559	4.94	0.0262
Harvest*Variety	6	BL516		1	0.1018	0.1329	-0.1586	0.3622	0.59	0.4436
Harvest*Variety	6	GEM		1	-0.0201	0.1403	-0.2950	0.2549	0.02	0.8863
Harvest*Variety	6	Hass		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	8	465418_99		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	8	465502_99		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	8	467352_00		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	8	BL516		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	8	GEM		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	8	Hass		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	10	EarlyGreen		1	0.4152	0.1983	0.0265	0.8040	4.38	0.0363
Harvest*Variety	10	Eugenin		1	0.1784	0.1775	-0.1694	0.5263	1.01	0.3147
Harvest*Variety	10	Flavia		1	0.2201	0.1768	-0.1264	0.5667	1.55	0.2131
Harvest*Variety	10	Hass		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	11	464918_99		1	0.2087	0.1556	-0.0963	0.5137	1.80	0.1799
Harvest*Variety	11	465518_99		1	0.3862	0.1421	0.1078	0.6647	7.39	0.0066
Harvest*Variety	11	EarlyGreen		1	-0.3601	0.1878	-0.7281	0.0080	3.68	0.0552
Harvest*Variety	11	Eugenin		1	-0.1018	0.1541	-0.4037	0.2002	0.44	0.5089
Harvest*Variety	11	Flavia		1	-0.1111	0.1546	-0.4140	0.1919	0.52	0.4723
Harvest*Variety	11	Hass		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	12	464918_99		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	12	465518_99		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	12	EarlyGreen		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	12	Eugenin		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	12	Flavia		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety	12	Hass		0	0.0000	0.0000	0.0000	0.0000	.	.
Wks	1			1	0.6337	0.0991	0.4396	0.8279	40.93	<.0001
Wks	3			1	0.2434	0.1069	0.0339	0.4530	5.18	0.0228
Wks	6			0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	1	1		1	0.1554	0.1227	-0.0852	0.3960	1.60	0.2055
Harvest*Wks	1	3		1	-0.0044	0.1337	-0.2663	0.2576	0.00	0.9739
Harvest*Wks	1	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	2	1		1	0.0039	0.1303	-0.2515	0.2594	0.00	0.9760
Harvest*Wks	2	3		1	-0.3369	0.1459	-0.6228	-0.0509	5.33	0.0209
Harvest*Wks	2	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	3	1		1	0.3787	0.1479	0.0888	0.6686	6.55	0.0105
Harvest*Wks	3	3		1	0.2919	0.1596	-0.0209	0.6046	3.34	0.0674
Harvest*Wks	3	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	4	1		1	0.3724	0.1431	0.0920	0.6528	6.78	0.0092
Harvest*Wks	4	3		1	0.2197	0.1551	-0.0843	0.5238	2.01	0.1566
Harvest*Wks	4	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	5	1		1	0.3980	0.1411	0.1214	0.6746	7.95	0.0048
Harvest*Wks	5	3		1	0.5058	0.1455	0.2205	0.7911	12.08	0.0005
Harvest*Wks	5	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	6	1		1	0.1930	0.1326	-0.0670	0.4529	2.12	0.1457
Harvest*Wks	6	3		1	0.0389	0.1443	-0.2439	0.3216	0.07	0.7876
Harvest*Wks	6	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	8	1		1	-0.0869	0.1298	-0.3414	0.1675	0.45	0.5031
Harvest*Wks	8	3		1	-0.0530	0.1400	-0.3273	0.2213	0.14	0.7051
Harvest*Wks	8	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	10	1		1	0.2085	0.1503	-0.0861	0.5030	1.92	0.1654
Harvest*Wks	10	3		1	0.4674	0.1573	0.1591	0.7757	8.83	0.0030
Harvest*Wks	10	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	11	1		1	0.1281	0.1270	-0.1208	0.3771	1.02	0.3131
Harvest*Wks	11	3		1	0.3782	0.1344	0.1148	0.6416	7.92	0.0049
Harvest*Wks	11	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	12	1		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	12	3		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Wks	12	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	464918_99	1		1	-0.4041	0.1463	-0.6908	-0.1175	7.64	0.0057
Variety*Wks	464918_99	3		1	0.0361	0.1509	-0.2596	0.3319	0.06	0.8107
Variety*Wks	464918_99	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	465418_99	1		1	0.2810	0.1245	0.0370	0.5250	5.10	0.0240
Variety*Wks	465418_99	3		1	-0.0069	0.1401	-0.2815	0.2677	0.00	0.9609
Variety*Wks	465418_99	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	465502_99	1		1	0.2196	0.1600	-0.0940	0.5331	1.88	0.1699
Variety*Wks	465502_99	3		1	-0.0060	0.1770	-0.3530	0.3409	0.00	0.9728
Variety*Wks	465502_99	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	465518_99	1		1	-0.6018	0.1503	-0.8964	-0.3072	16.03	<.0001
Variety*Wks	465518_99	3		1	0.1132	0.1499	-0.1806	0.4071	0.57	0.4501
Variety*Wks	465518_99	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	467352_00	1		1	-0.6158	0.1862	-0.9807	-0.2508	10.94	0.0009
Variety*Wks	467352_00	3		1	-0.7944	0.2142	-1.2142	-0.3746	13.76	0.0002
Variety*Wks	467352_00	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	BL516	1		1	0.2457	0.1133	0.0235	0.4678	4.70	0.0302
Variety*Wks	BL516	3		1	0.2937	0.1210	0.0566	0.5309	5.89	0.0152
Variety*Wks	BL516	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	EarlyGreen	1		1	-0.7673	0.1913	-1.1422	-0.3923	16.09	<.0001
Variety*Wks	EarlyGreen	3		1	-0.1257	0.1872	-0.4926	0.2413	0.45	0.5021
Variety*Wks	EarlyGreen	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	Eugenin	1		1	-0.3958	0.1522	-0.6940	-0.0975	6.76	0.0093
Variety*Wks	Eugenin	3		1	-0.2738	0.1631	-0.5934	0.0458	2.82	0.0932
Variety*Wks	Eugenin	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	Flavia	1		1	-0.4303	0.1532	-0.7306	-0.1301	7.89	0.0050
Variety*Wks	Flavia	3		1	-0.1640	0.1609	-0.4794	0.1514	1.04	0.3082
Variety*Wks	Flavia	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	GEM	1		1	0.6080	0.1210	0.3708	0.8453	25.24	<.0001
Variety*Wks	GEM	3		1	0.2092	0.1335	-0.0524	0.4708	2.46	0.1170
Variety*Wks	GEM	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	Hass	1		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	Hass	3		0	0.0000	0.0000	0.0000	0.0000	.	.
Variety*Wks	Hass	6		0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	464918_99	1	1	0.0732	0.1834	-0.2862	0.4326	0.16	0.6897
Harvest*Variety*Wks	1	464918_99	3	1	-0.2499	0.1940	-0.6301	0.1303	1.66	0.1977
Harvest*Variety*Wks	1	464918_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	465418_99	1	1	0.1227	0.1812	-0.2324	0.4777	0.46	0.4983
Harvest*Variety*Wks	1	465418_99	3	1	0.5621	0.1987	0.1726	0.9517	8.00	0.0047
Harvest*Variety*Wks	1	465418_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	465518_99	1	1	0.0893	0.1801	-0.2636	0.4422	0.25	0.6201
Harvest*Variety*Wks	1	465518_99	3	1	-0.2623	0.1840	-0.6230	0.0984	2.03	0.1541
Harvest*Variety*Wks	1	465518_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	BL516	1	1	-0.2545	0.1478	-0.5442	0.0351	2.97	0.0850
Harvest*Variety*Wks	1	BL516	3	1	-0.3831	0.1608	-0.6981	-0.0680	5.68	0.0172
Harvest*Variety*Wks	1	BL516	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	EarlyGreen	1	1	0.6960	0.2860	0.1353	1.2566	5.92	0.0150
Harvest*Variety*Wks	1	EarlyGreen	3	1	0.4462	0.2890	-0.1203	1.0127	2.38	0.1226
Harvest*Variety*Wks	1	EarlyGreen	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	Eugenin	1	1	-0.0276	0.2062	-0.4317	0.3766	0.02	0.8937
Harvest*Variety*Wks	1	Eugenin	3	1	-0.2985	0.2302	-0.7496	0.1527	1.68	0.1947
Harvest*Variety*Wks	1	Eugenin	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	Flavia	1	1	0.0955	0.2058	-0.3078	0.4988	0.22	0.6427
Harvest*Variety*Wks	1	Flavia	3	1	-0.4559	0.2299	-0.9065	-0.0053	3.93	0.0474
Harvest*Variety*Wks	1	Flavia	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	GEM	1	1	-0.3522	0.1821	-0.7091	0.0046	3.74	0.0531
Harvest*Variety*Wks	1	GEM	3	1	-0.4681	0.2099	-0.8794	-0.0567	4.97	0.0257
Harvest*Variety*Wks	1	GEM	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	Hass	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	Hass	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	1	Hass	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	2	464918_99	1	1	0.0012	0.1897	-0.3706	0.3729	0.00	0.9952
Harvest*Variety*Wks	2	464918_99	3	1	-0.2612	0.2060	-0.6649	0.1426	1.61	0.2049
Harvest*Variety*Wks	2	464918_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	2	465418_99	1	1	-0.0670	0.1736	-0.4071	0.2732	0.15	0.6995
Harvest*Variety*Wks	2	465418_99	3	1	0.3057	0.1972	-0.0808	0.6921	2.40	0.1211
Harvest*Variety*Wks	2	465418_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	2	465518_99	1	1	0.3453	0.1933	-0.0335	0.7241	3.19	0.0740
Harvest*Variety*Wks	2	465518_99	3	1	-0.1142	0.2044	-0.5148	0.2864	0.31	0.5764
Harvest*Variety*Wks	2	465518_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	2	BL516	1	1	-0.2304	0.1814	-0.5860	0.1252	1.61	0.2042
Harvest*Variety*Wks	2	BL516	3	1	-0.1019	0.2023	-0.4984	0.2946	0.25	0.6146
Harvest*Variety*Wks	2	BL516	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	2	Eugenin	1	1	0.2198	0.2093	-0.1904	0.6300	1.10	0.2936
Harvest*Variety*Wks	2	Eugenin	3	1	-0.0342	0.2389	-0.5023	0.4340	0.02	0.8863
Harvest*Variety*Wks	2	Eugenin	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	2	Flavia	1	1	0.2182	0.2122	-0.1976	0.6341	1.06	0.3037
Harvest*Variety*Wks	2	Flavia	3	1	-0.0808	0.2380	-0.5472	0.3857	0.12	0.7342
Harvest*Variety*Wks	2	Flavia	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	2	Hass	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	2	Hass	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	2	Hass	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	3	464918_99	1	1	0.2063	0.2382	-0.2606	0.6731	0.75	0.3865
Harvest*Variety*Wks	3	464918_99	3	1	-0.0934	0.2508	-0.5851	0.3983	0.14	0.7096
Harvest*Variety*Wks	3	464918_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	3	465418_99	1	1	-0.3191	0.2132	-0.7369	0.0987	2.24	0.1344
Harvest*Variety*Wks	3	465418_99	3	1	-0.1537	0.2357	-0.6158	0.3083	0.43	0.5143
Harvest*Variety*Wks	3	465418_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	3	465518_99	1	1	0.2591	0.2083	-0.1492	0.6674	1.55	0.2136
Harvest*Variety*Wks	3	465518_99	3	1	-0.3338	0.2157	-0.7564	0.0889	2.40	0.1217
Harvest*Variety*Wks	3	465518_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	3	BL516	1	1	0.0940	0.2216	-0.3404	0.5284	0.18	0.6715
Harvest*Variety*Wks	3	BL516	3	1	-0.1652	0.2404	-0.6364	0.3061	0.47	0.4921
Harvest*Variety*Wks	3	BL516	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	3	Eugenin	1	1	0.4497	0.2593	-0.0585	0.9579	3.01	0.0828
Harvest*Variety*Wks	3	Eugenin	3	1	0.7282	0.2707	0.1976	1.2587	7.24	0.0071
Harvest*Variety*Wks	3	Eugenin	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	3	Flavia	1	1	0.4206	0.2497	-0.0688	0.9099	2.84	0.0921
Harvest*Variety*Wks	3	Flavia	3	1	0.2295	0.2651	-0.2902	0.7491	0.75	0.3868
Harvest*Variety*Wks	3	Flavia	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	3	GEM	1	1	-1.0419	0.2069	-1.4474	-0.6363	25.36	<.0001
Harvest*Variety*Wks	3	GEM	3	1	-0.7140	0.2284	-1.1616	-0.2664	9.78	0.0018
Harvest*Variety*Wks	3	GEM	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	3	Hass	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	3	Hass	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	3	Hass	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	4	465418_99	1	1	-0.0310	0.2036	-0.4300	0.3680	0.02	0.8790
Harvest*Variety*Wks	4	465418_99	3	1	0.3169	0.2228	-0.1199	0.7536	2.02	0.1550
Harvest*Variety*Wks	4	465418_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	4	465518_99	1	1	0.7561	0.2474	0.2713	1.2410	9.34	0.0022
Harvest*Variety*Wks	4	465518_99	3	1	0.2178	0.2569	-0.2857	0.7213	0.72	0.3965
Harvest*Variety*Wks	4	465518_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	4	467352_00	1	1	0.2194	0.3272	-0.4219	0.8607	0.45	0.5025
Harvest*Variety*Wks	4	467352_00	3	1	0.5135	0.3631	-0.1982	1.2252	2.00	0.1573
Harvest*Variety*Wks	4	467352_00	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	4	BL516	1	1	-0.6029	0.1814	-0.9584	-0.2473	11.04	0.0009
Harvest*Variety*Wks	4	BL516	3	1	-0.5264	0.1958	-0.9102	-0.1426	7.23	0.0072
Harvest*Variety*Wks	4	BL516	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	4	Eugenin	1	1	0.1156	0.2886	-0.4501	0.6812	0.16	0.6888
Harvest*Variety*Wks	4	Eugenin	3	1	0.2160	0.3079	-0.3874	0.8194	0.49	0.4829
Harvest*Variety*Wks	4	Eugenin	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	4	Flavia	1	1	0.0999	0.2935	-0.4753	0.6752	0.12	0.7335
Harvest*Variety*Wks	4	Flavia	3	1	0.3038	0.3031	-0.2903	0.8979	1.00	0.3162
Harvest*Variety*Wks	4	Flavia	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	4	GEM	1	1	-0.8419	0.1841	-1.2028	-0.4810	20.90	<.0001
Harvest*Variety*Wks	4	GEM	3	1	-0.5824	0.2042	-0.9827	-0.1822	8.14	0.0043
Harvest*Variety*Wks	4	GEM	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	4	Hass	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	4	Hass	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	4	Hass	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	5	464918_99	3	1	-0.0728	0.2485	-0.5598	0.4142	0.09	0.7695
Harvest*Variety*Wks	5	464918_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	5	465418_99	1	1	-0.4081	0.1895	-0.7795	-0.0367	4.64	0.0313
Harvest*Variety*Wks	5	465418_99	3	1	-0.0884	0.1978	-0.4761	0.2992	0.20	0.6548
Harvest*Variety*Wks	5	465418_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	5	467352_00	1	1	-0.1440	0.2585	-0.6506	0.3625	0.31	0.5773
Harvest*Variety*Wks	5	467352_00	3	1	0.3075	0.2788	-0.2390	0.8540	1.22	0.2701
Harvest*Variety*Wks	5	467352_00	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	5	BL516	1	1	-1.2554	0.1939	-1.6355	-0.8753	41.91	<.0001
Harvest*Variety*Wks	5	BL516	3	1	-0.9924	0.1971	-1.3787	-0.6062	25.36	<.0001
Harvest*Variety*Wks	5	BL516	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	5	Eugenin	3	1	0.4296	0.2745	-0.1084	0.9677	2.45	0.1176
Harvest*Variety*Wks	5	Eugenin	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	5	Flavia	3	1	0.2838	0.3004	-0.3050	0.8726	0.89	0.3448
Harvest*Variety*Wks	5	Flavia	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	5	GEM	1	1	-1.2872	0.1803	-1.6405	-0.9339	50.98	<.0001
Harvest*Variety*Wks	5	GEM	3	1	-0.8069	0.1898	-1.1788	-0.4350	18.08	<.0001
Harvest*Variety*Wks	5	GEM	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	5	Hass	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	5	Hass	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	5	Hass	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	6	465418_99	1	1	-0.1943	0.1824	-0.5519	0.1633	1.13	0.2869
Harvest*Variety*Wks	6	465418_99	3	1	0.1395	0.2022	-0.2567	0.5357	0.48	0.4901
Harvest*Variety*Wks	6	465418_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	6	467352_00	1	1	0.2309	0.2810	-0.3198	0.7816	0.68	0.4112
Harvest*Variety*Wks	6	467352_00	3	1	0.6174	0.3122	0.0055	1.2294	3.91	0.0480
Harvest*Variety*Wks	6	467352_00	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	6	BL516	1	1	-0.7421	0.1656	-1.0667	-0.4176	20.09	<.0001
Harvest*Variety*Wks	6	BL516	3	1	-0.4293	0.1772	-0.7765	-0.0820	5.87	0.0154
Harvest*Variety*Wks	6	BL516	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	6	GEM	1	1	-0.8934	0.1700	-1.2265	-0.5602	27.63	<.0001
Harvest*Variety*Wks	6	GEM	3	1	-0.4018	0.1871	-0.7685	-0.0351	4.61	0.0318
Harvest*Variety*Wks	6	GEM	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	6	Hass	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	6	Hass	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	6	Hass	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	465418_99	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	465418_99	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	465418_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	465502_99	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	465502_99	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	465502_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	467352_00	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	467352_00	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	467352_00	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	BL516	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	BL516	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	BL516	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	GEM	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	GEM	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	GEM	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	Hass	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	Hass	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	8	Hass	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	10	EarlyGreen	1	1	-0.0410	0.2683	-0.5669	0.4848	0.02	0.8785
Harvest*Variety*Wks	10	EarlyGreen	3	1	-0.5738	0.2669	-1.0968	-0.0507	4.62	0.0316
Harvest*Variety*Wks	10	EarlyGreen	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	10	Eugenin	1	1	0.1558	0.2222	-0.2798	0.5913	0.49	0.4834
Harvest*Variety*Wks	10	Eugenin	3	1	-0.1516	0.2348	-0.6118	0.3086	0.42	0.5186
Harvest*Variety*Wks	10	Eugenin	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	10	Flavia	1	1	0.0240	0.2238	-0.4147	0.4626	0.01	0.9148
Harvest*Variety*Wks	10	Flavia	3	1	-0.2080	0.2315	-0.6618	0.2458	0.81	0.3690
Harvest*Variety*Wks	10	Flavia	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	10	Hass	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	10	Hass	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	10	Hass	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	11	464918_99	1	1	0.1158	0.1978	-0.2720	0.5036	0.34	0.5583
Harvest*Variety*Wks	11	464918_99	3	1	-0.2155	0.2024	-0.6121	0.1812	1.13	0.2870
Harvest*Variety*Wks	11	464918_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	11	465518_99	1	1	-0.1024	0.1862	-0.4675	0.2626	0.30	0.5823
Harvest*Variety*Wks	11	465518_99	3	1	-0.6018	0.1862	-0.9667	-0.2368	10.45	0.0012
Harvest*Variety*Wks	11	465518_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	11	EarlyGreen	1	1	0.8493	0.2453	0.3686	1.3299	11.99	0.0005
Harvest*Variety*Wks	11	EarlyGreen	3	1	0.4322	0.2418	-0.0417	0.9062	3.19	0.0739
Harvest*Variety*Wks	11	EarlyGreen	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	11	Eugenin	1	1	0.3409	0.1944	-0.0401	0.7218	3.08	0.0795
Harvest*Variety*Wks	11	Eugenin	3	1	0.3142	0.2041	-0.0858	0.7141	2.37	0.1236
Harvest*Variety*Wks	11	Eugenin	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	11	Flavia	1	1	0.3416	0.1958	-0.0420	0.7253	3.05	0.0809
Harvest*Variety*Wks	11	Flavia	3	1	0.1713	0.2029	-0.2265	0.5690	0.71	0.3987
Harvest*Variety*Wks	11	Flavia	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	11	Hass	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	11	Hass	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	11	Hass	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	464918_99	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	464918_99	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	464918_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	465518_99	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	465518_99	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	465518_99	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	EarlyGreen	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	EarlyGreen	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	EarlyGreen	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	Eugenin	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	Eugenin	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	Eugenin	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	Flavia	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	Flavia	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	Flavia	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	Hass	1	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	Hass	3	0	0.0000	0.0000	0.0000	0.0000	.	.
Harvest*Variety*Wks	12	Hass	6	0	0.0000	0.0000	0.0000	0.0000	.	.
Dispersion				1	0.0000	0.0005	.	.

[StatDave · Accepted solution]

The significant test (using SCALE=0 and NOSCALE) seems odd if the dispersion parameter estimate (I assume from NOT using SCALE=0 NOSCALE), 0.0000, is accurate. I suspect that the problem causing the warning message might have affected that estimate and prevents confidence limits appearing for it. I think it would be useful to fit the model using DIST=POISSON and look at the Value/DF values for the deviance and Pearson statistics. If that avoids the warning and the Value/DF values are not close to 2 or more, then that is likely reasonable to use this Poisson model rather than the negative binomial model. Then if some of the type3 tests for the interactions are not significant, you could simplify the model to lessen the number of parameters.

If the Value/DF values still indicate overdispersion, then you could try other models to adjust for it besides the negative binomial as discussed and illustrated in this note.

[palolix]

Yes, the warning with the 0.000 was from the model without the scale statement.

I tried Poisson and I don't get the warning. Also, Value/DF for deviance and Person are less than 2 and all type3 tests for the interactions are significant. Thank you so much StatDave!

proc genmod data=one;
class Harvest Variety Wks;
model DTR=Harvest|Variety|Wks/type3 dist=poisson link=log;
/*slice Harvest*Variety*Wks/sliceby=Harvest*Wks diff adjust=simulate(seed=1);*/
run;

Criteria For Assessing Goodness Of Fit
Criterion	DF	Value	Value/DF
Deviance	6018	2669.0119	0.4435
Scaled Deviance	6018	2669.0119	0.4435
Pearson Chi-Square	6018	2651.8346	0.4407
Scaled Pearson X2	6018	2651.8346	0.4407
Log Likelihood		36356.2831
Full Log Likelihood		-12484.2748
AIC (smaller is better)		25364.5496
AICC (smaller is better)		25377.6465
BIC (smaller is better)		26698.0562

Algorithm converged.

Question: If I find overdispersion and I don't get any warning when using negbin, is it still preferably to use Poisson as long as the Value/DF for deviance and Person are less than 2? 

[StatDave]

If you find evidence of overdispersion, either from a too large Value/DF or from the test using SCALE=0 and NOSCALE with DIST=NEGBIN, then that suggests that the distribution is not Poisson and something else should be used like in the note I referred to. The warnings don't play into it. There is no hard and fast cutoff criterion on the Value/DF. 

[palolix]

Ok makes sense, thank you very much for the great help!