In the context of experimental design, which of the following best describes a controlled variable?

• A. A factor that is kept constant throughout the experiment to ensure that any observed effect is due to the independent variable.
• B. A factor that is intentionally changed to observe its effect on the dependent variable.
• C. A factor that is measured as the outcome of the experiment.
• D. A variable that is not considered or monitored during the experiment.

Answer: (A)

Verified step by step guidance

1. Understand the concept of a controlled variable: A controlled variable is a factor in an experiment that is kept constant to ensure that any observed changes in the dependent variable are solely due to the manipulation of the independent variable.
2. Differentiate between the independent variable, dependent variable, and controlled variable: The independent variable is the factor intentionally changed to observe its effect, the dependent variable is the factor measured as the outcome, and the controlled variable is kept constant.
3. Analyze the options provided: Identify which option aligns with the definition of a controlled variable. For example, the option stating 'A factor that is kept constant throughout the experiment to ensure that any observed effect is due to the independent variable' matches the definition.
4. Eliminate incorrect options: Discard options that describe the independent variable ('A factor that is intentionally changed'), the dependent variable ('A factor that is measured as the outcome'), or irrelevant factors ('A variable that is not considered or monitored').
5. Conclude the correct answer based on the analysis: The correct description of a controlled variable is the one that ensures experimental consistency by remaining constant throughout the experiment.