Final answer:
The independent variable is manipulated by the researcher, the dependent variable is measured in response, and it is advisable to have only one dependent variable to clearly determine cause-effect relationships. Control variables are constants in an experiment, crucial for ensuring that observed effects are due to the independent variable alone.
Step-by-step explanation:
The difference between an independent variable and a dependent variable is that the independent variable is the one that is intentionally changed or manipulated by the researcher to observe its effect on the dependent variable, which is the variable being measured or tested in response to the independent variable. In an experiment, you generally want to have only one dependent variable, as having more can make it difficult to determine which independent variable is causing any observed changes.
Control variables are conditions that are kept constant and unchanging. They are a critical part of scientific experiments because they ensure that any observed effect on the dependent variable is indeed due to the manipulation of the independent variable and not some other extraneous factor.