I'm using regression as ancova in R as below. Condition is coded: 0 = control, and 1 = experimental.

I understand that the intercept is the adjusted mean for the control and the intercept + condition coefficient is the adjusted mean for the experimental group.

My question is, can i calculate the SE of these adjusted means in the same way?

i.e. can i report this:

Control adj M (SE)

6.91 (2.55)

Experimental adj M (SE)

11.83 (3.85)

cheers

Tim

Call:

lm(formula = X.STAIpost. ~ X.STAIpre. + X.Condition.)

Coefficients:

Estimate Std. Error t value Pr(>|t|)

(Intercept) 6.91183 2.55222 2.708 0.008039 **

X.STAIpre. 0.83641 0.06353 13.165 < 2e-16 ***

X.Condition. 4.92851 1.29853 3.795 0.000261 ***

---

Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 6.394 on 94 degrees of freedom

(3 observations deleted due to missingness)

Multiple R-squared: 0.6647, Adjusted R-squared: 0.6576

F-statistic: 93.19 on 2 and 94 DF, p-value: < 2.2e-16