Hi,

I am trying to get an output data set from proc logistic containing the odd ratio estimates and the confidence intervals for them.

The independent variable of interest has 4 classes so 3 of the classes are compared with the benchmark class (in my case the lowest category).

According with SAS documentation, I was able to compute the odds-ratios for the three parameters:

ref_vs_3=round(exp(2*&exposure.3+&exposure.2+&exposure.1),.001);

ref_vs_2=round(exp(&exposure.1+2*&exposure.2+&exposure.3),.001);

ref_vs_1=round(exp(&exposure.3+&exposure.2+2*&exposure.1),.001);

Where exposure3, exposure2, and exposure1 are the coefficients produced by the logistic regression (my values are identical to the ones in the SAS output).

However, I do have problems computing the confidence intervals for these odds ratios.

According to SAS documentation, it would be = exp(coeff_j +/_ z*sqrt (variance_j). And the variance is available in the output when using covout option.

I tried but I am getting totally different results.

Any help would be more than welcomed.

Thank you very much!

Cornel Lencar, MF

Data Analyst

School of Occupational and Environmental Hygiene, UBC

#340-2206 East Mall, Vancouver, BC V6T 1Z4

Phone: 604-822-0839

E-mail: clencar@interchange.ubc.ca