T-test by options - continuous variable

[Nur Eken]

Hi,

I'm trying to find out if a "delta" between two variables across time can be explained by another variable. Initially, I wrote the following code which worked:
ttest (difference), by (indvar)
but the independent variable I want to use now is continuous, which is not allowed in this option set. Is there a way to add continuous variable as a qualifier in the ttest?

Thank you,

[Rich Goldstein]

no, but you can get the same effect by using -regress- (recall that when the "by" variable is binary; the t-test and regression with an indicator variable are exactly the same thing; compare

sysuse auto
ttest gear, by(foreign)
regress gear i.foreign

[Nur Eken]

Thank you!

[Nur Eken]

On a related note, I wanted to visualize means difference in a paired sample ttest, with whiskers and statistical significance noted. Is there a way to do this with bar graph? In the options I don't seem to find a way to indicate the statistical significance. Thanks!