In a scientific experiment, an independent variable is the factor that is intentionally changed or manipulated by the researcher. It's the "cause" in a cause-and-effect relationship being investigated.

Here are some key points about independent variables:

* Controlled: The researcher directly controls the levels or values of the independent variable.

* Manipulated: The independent variable is actively changed to see its impact on the dependent variable.

* Influences: The independent variable is believed to have a direct influence on the dependent variable.

* Measured: The independent variable is often measured and recorded.

Example:

In an experiment testing the effect of different fertilizer types on plant growth, the independent variable is the type of fertilizer used. The researcher will manipulate this variable by using different fertilizer types on different plant groups.

Remember: The independent variable is what the researcher changes or manipulates to observe its impact on the dependent variable.