Hakeem is testing the effects of sunlight on samples of soil. which of these actions would introduce confounding variables into hakeem’s experiment?
he tests a theory that’s already been established.
he tests multiple hypotheses at a time.
he uses identical specimens when completing multiple trials.
he adjusts the independent variable and records the effects.
he uses different types of soil in each of his samples.

A confounding variable refers to an external effect, which modifies the influence of an independent and dependent variable. This extraneous effect is used to affect the outcome of an experimental design. The confounding variables can ruin the experiment and can generate unnecessary outcomes.  

In the given case, confounding variables can be introduced by testing multiple hypotheses at a time and by using distinct kinds of soil in each of the samples.  

the framers of the constitution insisted that federal judges be nominated instead of elected due to their desire to have judges above the shifting whims of the masses.

the hope, whether achieved or not, was that federal judges would only be beholden to the law and that by not having judges be elected, they would be protected if that law dictated an outcome that ran counter to popular opinion.