In a scientific study, which variable would be considered independent?

In a scientific study, the independent variable is the one that is manipulated or changed by the researcher to observe its effects on another variable, known as the dependent variable. This manipulation allows the researcher to identify relationships between the variables, helping to determine causality. For example, if a researcher is investigating the effect of different amounts of sunlight on plant growth, the amount of sunlight would be the independent variable, as the researcher alters it to see how it influences plant height or health.

The other options describe different roles of variables in an experiment. The dependent variable is influenced by changes in the independent variable, while constants refer to factors kept the same throughout the experiment to ensure that any observed effects are due to manipulation of the independent variable alone. Unchanged variables can clarify what is being studied but do not actively contribute to the experimentation as independent variables do. Understanding this distinction is crucial for conducting controlled scientific experiments effectively.