sas covariates in a linear regressions
<p>I am running a simple linear regression in SAS. The regression has three different groups of participants as the predictors (with group 1 as the reference), the outcome a continuous social support variable, and five covariates. Three of the covariates are dichotomized (<code>age</code>, <code>sex</code>, &amp; <code>education</code>), one is a three-level nominal variable (<code>marital status</code>), and the last is continuous (it's a <code>chronic disease index</code>). </p>

<p>My question is: <strong>Do I need to specify the different types of covariates in the SAS coding somehow?</strong></p>

<p>Would this coding example be correct?:</p>

<pre><code>proc glm data=work.example;

class group age sex education marital education chronic_diseases;

model social_support = group age sex education marital education chronic_diseases;

estimate 'group 1 vs group 2' group -1 1 0;

estimate 'group 1 vs group 3' group -1 0 1;

run;
</code></pre>