What is measured directly in an experiment as a response to changes made by the independent variable?

The dependent variable is the correct answer because it is specifically defined as the variable that is measured in an experiment in response to the manipulations of the independent variable. When researchers set up an experiment, they alter or control the independent variable to observe how it affects the dependent variable. Essentially, the dependent variable reflects the outcome or effects of the changes made, allowing scientists to analyze the relationship between the two variables.

For example, if an experiment is designed to test how different amounts of sunlight affect plant growth, the amount of growth (measured in height or biomass) is the dependent variable that responds to the changes in the independent variable of sunlight exposure. This direct measurement is crucial for drawing conclusions about the impact of the independent variable on the dependent variable.

Other variable types, like controlled variables, are factors kept constant throughout the experiment to ensure that any changes in the dependent variable are solely due to the manipulation of the independent variable. Extraneous variables are outside factors that could inadvertently influence the results, but they are not directly measured as part of the dependent variable. The independent variable, on the other hand, is the factor that the experimenter changes, not what is measured.