SAS Programming

DATA Step, Macro, Functions and more
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-white.png

Our biggest data and AI event of the year.

Don’t miss the livestream kicking off May 7. It’s free. It’s easy. And it’s the best seat in the house.

Join us virtually with our complimentary SAS Innovate Digital Pass. Watch live or on-demand in multiple languages, with translations available to help you get the most out of every session.

 

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.

SAS Training: Just a Click Away

 Ready to level-up your skills? Choose your own adventure.

Browse our catalog!

Discussion stats
  • 3 replies
  • 1275 views
  • 1 like
  • 3 in conversation