Question

which statement best describes the variables in a controlled experiment?
the independent variable is changed to see its effect on the dependent variable while all other conditions are unchanged
the dependent variable is changed to see its effect on the independent variable while all other conditions are unchanged
the independent variable is allowed to change, and the dependent variable is held constant to see what other conditions show a relationship
the dependent variable is allowed to change, and the independent variable is held constant to see what other conditions show a relationship

Explanation:

In a controlled experiment, the independent variable is the one manipulated by the experimenter to observe its impact on the dependent variable. All other factors are kept constant to isolate the effect of the independent - variable.

Answer:

The independent variable is changed to see its effect on the dependent variable while all other conditions are unchanged.