Question

identify the variables in an experiment and classify each as independent, dependent or controlled variables. (pp.15-18 will help)

1. an independent variable is
2. the dependent variable is

are those things that must not change throughout in order for the

Explanation:

For question 3, in experimental design (a concept in Natural Science, specifically in scientific method which is foundational across subfields like Biology, Chemistry, Physics etc.), an independent variable is the factor that is deliberately changed or manipulated by the experimenter to observe its effect on another variable. It's the "cause" in a cause - effect relationship within the experiment.
For question 4, the dependent variable is the factor that is observed or measured in an experiment. Its value depends on the changes made to the independent variable, so it's the "effect" that we are interested in measuring to see how it responds to the independent variable.

Answer:

1. An independent variable is the variable that is deliberately manipulated or changed by the experimenter in an experiment to observe its impact on another variable.
2. The dependent variable is the variable that is observed and measured in an experiment, and its value depends on the independent variable.