If we do not observe a sufficiently large between-groups variance, then we have not observed __________
experimenter effects, an effect of the dependent variable, enough samples, or an effect of the independent variable
I believe - enough samples - is the answer.
You are incorrect in your belief. If you do not observe a sufficiently large between-groups variance, this means that there is not a significant variability due to treatment effects.
When we conduct experiments in ...
This job targets effect of the independent variable.