Imagine that we are interested in how maternal separation affects stress early in life. to explore this relationship, we randomly assign young rat pups to either be separated from their mothers for 8 hours per day or to remain with their mothers all day. we then measure corticosterone levels (a hormonal marker of stress) in all of the rat pups at the end of the day. what is the independent variable? acorticosterone levelsbstress experienced by rat pupscmaternal separationdyoung rat pups

The independent variable in this case is maternal separation.

Explanation:

The difference in the levels of corticosterone measured in the rat pups is evidently due to the stress caused to them. The invariable reason the stress is caused is the separation of the rat pups from their mother. The similarity in the levels of corticosterone in rat pups not separated from the mother and the similarity in the corticosterone levels of the ones separated from their mothers is proof enough that the levels of corticosterone or the age of the pups are not independent variables.