Covariate in a paired t-test

[fabstat]

Hi,
I'm surprised by results, that made me wonder how Jamovi realised a paired t-test with a covariate.

I realised a paired samples t-test, and there was a non-significant effect of time.
I introduced a quantitative covariate, and there is a significant effect of time, of covariate and of interaction x covariate.

Is there an application condition to be able to introduce a covariate in the paired t-test, like there is an ANCOVA?
The scatterplot of the difference of DV time 1 - time 2 with the covariate shows no linear relationship.

Thank you for your help.
Fabienne

[mcfanda@gmail.com]

Ancova with a paired (repeated measures) factor with two levels is a paired t-test with covariates. The results would be identical. If you have a repeated-measures factor with 2 levels, run the ANCOVA, take the square root of the F-test, and that is the t-test you would obtain in a "paired t-test with covariates". P-values would be identical.