```Date: Tue, 18 Jun 2002 15:54:37 +0100 Reply-To: david.mcnulty@QUESTINTL.COM Sender: "SAS(r) Discussion" From: david.mcnulty@QUESTINTL.COM Subject: Untenable results from PROC GENMOD Content-type: text/plain; charset=us-ascii Hi Folks, I am trying to estimate some proportions in a three way table using Proc GENMOD and am getting some very curious results. In brief after back transforming the estimated LSMeans, the proportions have standard errors greater than 1. Example: LSmean Prod_1 = 2.1478, se = 1622.330 proportion = Exp(mu)/(1+Exp(mu))= 0.895 approx se = p(1-p).SE(LSMean) = 151.86 (Since n is 31, the se using the approximation sqrt(p(1-p)/n) is closer to 0.05) Is there something I can tweak in Proc GENMOD to get some sensible answers? Thanks Dave. Additional Info ================ In the following code the binomial response "correct" has the form 1 or 0 rather than the alternate events/trial syntax. Product "Prod_8" is excluded from the analysis since the empirical proportion for Product="Prod_8" and phase="P3" is one. Since log(1/(1-1)) is undefined SAS warns the Hessian is not positive definite and refuses to calculate the remaining LSMeans. Code ==== proc genmod data=master descending; class subject phase product; model correct=subject phase|product / type1 type3 dist=bin; lsmeans phase|product ; where product ne 'Prod_8'; quit; Sample Output ============= The SAS System 10:57 Tuesday, June 18, 2002 126 The GENMOD Procedure LR Statistics For Type 3 Analysis Chi- Source DF Square Pr > ChiSq Subject 30 58.02 0.0016 Phase 1 0.17 0.6775 Product 6 26.30 0.0002 Phase*Product 6 2.97 0.8124 Least Squares Means Standard Chi- Effect Phase Product Estimate Error DF Square Pr > ChiSq Phase P2 1.9958 1622.330 1 0.00 0.9990 Phase P3 2.1003 1622.330 1 0.00 0.9990 Product Prod_1 2.1478 1622.330 1 0.00 0.9989 Product Prod_2 2.7500 1622.330 1 0.00 0.9986 Product Prod_3 2.3726 1622.330 1 0.00 0.9988 Product Prod_4 1.5691 1622.330 1 0.00 0.9992 Product Prod_5 0.8329 1622.330 1 0.00 0.9996 Product Prod_6 2.4147 1622.330 1 0.00 0.9988 Product Prod_7 2.2489 1622.330 1 0.00 0.9989 Phase*Product P2 Prod_1 2.3594 1622.330 1 0.00 0.9988 Phase*Product P2 Prod_2 2.6068 1622.330 1 0.00 0.9987 Phase*Product P2 Prod_3 2.6068 1622.330 1 0.00 0.9987 Phase*Product P2 Prod_4 1.5691 1622.330 1 0.00 0.9992 Phase*Product P2 Prod_5 0.7539 1622.330 1 0.00 0.9996 Phase*Product P2 Prod_6 1.9362 1622.330 1 0.00 0.9990 Phase*Product P2 Prod_7 2.1384 1622.330 1 0.00 0.9989 Phase*Product P3 Prod_1 1.9362 1622.330 1 0.00 0.9990 Phase*Product P3 Prod_2 2.8933 1622.330 1 0.00 0.9986 ETC ... IMPORTANT NOTICE: This email is confidential, may be legally privileged, and is for the intended recipient only. Access, disclosure, copying, distribution, or reliance on any of it by anyone else is prohibited and may be a criminal offence. Please delete if obtained in error and email confirmation to the sender. ```

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