Final answer:
In an experiment, the variable observed that changes in response to a test is the dependent variable, while the one manipulated by the researcher is the independent variable.
Step-by-step explanation:
In an experiment, the variable that you observe which changes in response to something the scientist is testing is known as the dependent variable. The independent variable is manipulated or controlled by the researcher, and its impact is measured by observing changes in the dependent variable. To ensure that the result of an experiment is attributable to the independent variable, control variables are kept constant, and often a control group is used which does not receive the experimental treatment for comparison purposes.
As an example, if a scientist is studying the effect of sunlight on plant growth, the amount of sunlight (independent variable) is altered, and the effect on plant growth (dependent variable) is measured. All other factors like water, soil type, and plant species that could affect growth are kept the same across all test samples to ensure accuracy and relevance.