Suppose we have two samples (A and B) of 200 people each. There are 100 men and 100 women in each population.
The income difference between men and women in A is 1000 dollars (per month). The difference in income between men and women in B is 500 dollars. (both differences are statistically significant)
Under what conditions (and via what kind of tests) can we say that the difference in income between men and women in A is significantly different from the difference in income in group B?
Sorry for a very naive question. Any hint/point to the right direction will be welcome.