Experimentation involves conducting tests to verify a hypothesis. Variables are measurable characteristics, factors, or parameters that can be modified or changed in an experiment and influence its results. Examples given include the effect of different soil types on plant height, and artificial versus organic fertilizer on fruit yield.

There are three types of variables: independent, dependent, and controlled. Independent variables, also known as manipulated variables, are the factors or conditions that are intentionally changed by the experimenter. They are the 'cause' of any observed changes. For instance, the type of fertilizer used is an independent variable.

Dependent variables, also called responding variables, are affected by the changes made to the independent variable. They are the factors or conditions measured or observed, representing the 'effect' of the independent variable. In the fertilizer example, the number of fruits yielded is the dependent variable.

Controlled variables are kept constant or unchanged throughout an experiment. These variables are maintained consistently to ensure they do not influence the outcome, allowing for a clear understanding of the relationship between the independent and dependent variables.

A scenario is presented where a researcher named Eon studies the effect of food amount on tilapia fish weight. The independent variable is the amount of food given, the dependent variable is the weight of the tilapia, and the controlled variables are the type of food and the size of the tanks.

Another scenario involves Christine investigating the effectiveness of different fertilizer brands on corn plant fruit yield. The independent variable is the brand of fertilizer, the dependent variable is the number of fruits yielded, and the controlled variables are the amount of fertilizer, water, and sunlight.

The video concludes by reiterating the definitions: independent variables are manipulated changes, dependent variables are the resulting effects, and controlled variables are conditions kept constant throughout the experiment.