In an experiment, what is the independent variable?

In an experiment, the independent variable is the one that is manipulated by the researcher to observe its effects on other variables. This manipulation allows the researcher to establish a cause-and-effect relationship. By changing the independent variable, the experimenter can investigate how it influences the dependent variable, which is measured or observed to see if any changes occur as a result of this manipulation. This basic principle of experimental design is crucial for drawing valid conclusions regarding the relationship between variables.

The other options describe different aspects of experimental design, such as the dependent variable, which is what is observed and measured, and external factors, which may affect results but are not the primary focus of the manipulation. Understanding the role of the independent variable is fundamental in structuring an experiment and interpreting its outcomes effectively.