topic Possible bug in Proc Surveylogistic program? in Statistical Procedures

Possible bug in Proc Surveylogistic program?

ngordon_kpdor — Wed, 06 Dec 2017 00:02:48 GMT

When I run the following below using a class variable, I get the same odds ratios for my race/ethnic groups compared to the reference group as I get when I run the model using indicator variables. However, despite getting the same ORs and CLs, all of the ORs have a p-value <.01 when I use the model with indicator variables, whereas the p-values for the same ethnic groups in the model using the class variable are not all significant even though the CLs around the ORs make them seem like they should be. Is this a bug in the program? Should I avoid class variables for variables I need to test for significance?

Proc surveylogistic; strata x;

class ethnicity (ref='White');

model exvghlth(descending)=ethnicity;

weight wgtfac;

format ethnicity ethnicity.;

run;

vs.

proc surveylogistic; strata x;

model exvghlth(descending)=black asianpi Hispanic;

weight wgtfac;

run;

Results from class variable model:

Analysis of Maximum Likelihood Estimates

Standard Wald

Parameter DF Estimate Error Chi-Square Pr > ChiSq

Intercept 1 0.0140 0.0215 0.4271 0.5134

ethnicity Asian/PI 1 0.0360 0.0363 0.9819 0.3217

ethnicity Black 1 -0.2356 0.0385 37.5352 <.0001

ethnicity Hispanic 1 -0.00728 0.0423 0.0297 0.8633

Odds Ratio Estimates

Point 95% Wald

Effect Estimate Confidence Limits

ethnicity Asian/PI vs White 0.843 0.761 0.934

ethnicity Black vs White 0.642 0.576 0.716

ethnicity Hispanic vs White 0.807 0.717 0.909

Results from indicator variable model:

Analysis of Maximum Likelihood Estimates

Standard Wald

Parameter DF Estimate Error Chi-Square Pr > ChiSq

Intercept 1 0.2210 0.0320 47.8226 <.0001

asianpi 1 -0.1709 0.0523 10.6866 0.0011

black 1 -0.4425 0.0553 64.1436 <.0001

hispanic 1 -0.2142 0.0606 12.5022 0.0004

Odds Ratio Estimates

Point 95% Wald

Effect Estimate Confidence Limits

asianpi 0.843 0.761 0.934

black 0.642 0.576 0.716

hispanic 0.807 0.717 0.909

Re: Possible bug in Proc Surveylogistic program?

Reeza — Wed, 06 Dec 2017 00:50:23 GMT

Add parameter=Ref to your class variables?

@ngordon_kpdor wrote:

When I run the following below using a class variable, I get the same odds ratios for my race/ethnic groups compared to the reference group as I get when I run the model using indicator variables. However, despite getting the same ORs and CLs, all of the ORs have a p-value <.01 when I use the model with indicator variables, whereas the p-values for the same ethnic groups in the model using the class variable are not all significant even though the CLs around the ORs make them seem like they should be. Is this a bug in the program? Should I avoid class variables for variables I need to test for significance?

Proc surveylogistic; strata x;

class ethnicity (ref='White');

model exvghlth(descending)=ethnicity;

weight wgtfac;

format ethnicity ethnicity.;

run;

vs.

proc surveylogistic; strata x;

model exvghlth(descending)=black asianpi Hispanic;

weight wgtfac;

run;

Results from class variable model:

                 Analysis of Maximum Likelihood Estimates

                                         Standard          Wald

Parameter             DF    Estimate       Error    Chi-Square    Pr > ChiSq

Intercept               1      0.0140      0.0215        0.4271        0.5134

ethnicity Asian/PI     1      0.0360      0.0363        0.9819        0.3217

ethnicity Black       1     -0.2356      0.0385       37.5352        <.0001

ethnicity Hispanic   1    -0.00728      0.0423        0.0297        0.8633

                     Odds Ratio Estimates

                                   Point          95% Wald

Effect                         Estimate      Confidence Limits

ethnicity Asian/PI vs White       0.843       0.761       0.934

ethnicity Black   vs White       0.642       0.576       0.716

ethnicity Hispanic vs White       0.807       0.717       0.909

Results from indicator variable model:

             Analysis of Maximum Likelihood Estimates

                               Standard          Wald

Parameter   DF    Estimate       Error    Chi-Square    Pr > ChiSq

Intercept     1      0.2210      0.0320       47.8226        <.0001

asianpi       1     -0.1709      0.0523       10.6866        0.0011

black         1     -0.4425      0.0553       64.1436        <.0001

hispanic     1     -0.2142      0.0606       12.5022        0.0004

            Odds Ratio Estimates

               Point          95% Wald

Effect     Estimate      Confidence Limits

asianpi       0.843       0.761       0.934

black         0.642       0.576       0.716

hispanic       0.807      0.717       0.909