BookmarkSubscribeRSS Feed
☑ This topic is solved. Need further help from the community? Please sign in and ask a new question.
superbug
Quartz | Level 8

I am trying to model the data using a two-level model. Student nested in school. My dependent variable "pass" is dichotomously coded (1, 0). My  independent variable includes both dichotomously coded variable first and status (1, 0) and continuous variable "practice score"  as below

PROC GLIMMIX
DATA=pred METHOD=LAPLACE NOCLPRINT;
CLASS SCHOOLNUM;
MODEL PASS (EVENT="1")=first practice_score status/CL DIST=BINARY LINK=LOGIT SOLUTION;
RANDOM INTERCEPT/ SUBJECT=SCHOOLNUM S CL TYPE=VC;
COVTEST /WALD;
run;

Based on the fixed effects estimates as in the picture below, the probability of pass for first=1, status=1, is exp(-5.7755+0.7758+0.00872461.1849)/(1+exp(-5.7755+0.7758+0.008724+1.1849))=0.02175, which is too low from expected.  

 

superbug_1-1685993623210.png

 

Where was wrong with my SAS code above? Any help would be much appreciated. Thanks!

1 ACCEPTED SOLUTION

Accepted Solutions
PaigeMiller
Diamond | Level 26

Your formula is wrong. For each observation that you want a prediction, you want to use the values of the independent variables, which you are not doing. See Wikipedia or any textbook for the formula to predict: https://en.wikipedia.org/wiki/Multinomial_logistic_regression

 

The easiest way to predict the probability of passing is to use GLIMMIX, use the OUTPUT statement to have SAS compute the predicted probabilities. https://documentation.sas.com/doc/en/pgmsascdc/9.4_3.4/statug/statug_glimmix_syntax19.htm

--
Paige Miller

View solution in original post

3 REPLIES 3
PaigeMiller
Diamond | Level 26

Your formula is wrong. For each observation that you want a prediction, you want to use the values of the independent variables, which you are not doing. See Wikipedia or any textbook for the formula to predict: https://en.wikipedia.org/wiki/Multinomial_logistic_regression

 

The easiest way to predict the probability of passing is to use GLIMMIX, use the OUTPUT statement to have SAS compute the predicted probabilities. https://documentation.sas.com/doc/en/pgmsascdc/9.4_3.4/statug/statug_glimmix_syntax19.htm

--
Paige Miller
Rick_SAS
SAS Super FREQ

The variable names and the values first=1 and status=1 make me wonder whether the FIRST and STATUS variables are binary classification variables? If so, you should add them to the CLASS statement.

sas-innovate-2024.png

 

Secure your spot at the must-attend AI and analytics event of 2024: SAS Innovate 2024! Get ready for a jam-packed agenda featuring workshops, super demos, breakout sessions, roundtables, inspiring keynotes and incredible networking events.

 

Register by March 1 to snag the Early Bird rate of just $695! Don't miss out on this exclusive offer. 

 

Register now!

How to Concatenate Values

Learn how use the CAT functions in SAS to join values from multiple variables into a single value.

Find more tutorials on the SAS Users YouTube channel.

Click image to register for webinarClick image to register for webinar

Classroom Training Available!

Select SAS Training centers are offering in-person courses. View upcoming courses for:

View all other training opportunities.

Discussion stats
  • 3 replies
  • 304 views
  • 1 like
  • 3 in conversation