1. Independent Variable: This is the variable that the researcher *manipulates* or changes in an experiment. It's the factor you're testing the effect of.
* Example: In an experiment testing the effect of fertilizer on plant growth, the independent variable would be the amount of fertilizer applied.
2. Dependent Variable: This is the variable that is *measured* or observed in response to changes in the independent variable. It's what you're trying to find out about.
* Example: In the fertilizer experiment, the dependent variable would be the height of the plants.
3. Controlled Variable: These are all the factors that are kept *constant* throughout an experiment. They are important because they prevent other variables from influencing the results and ensure the experiment is fair.
* Example: In the fertilizer experiment, controlled variables might include the type of plant used, the amount of water given, and the temperature of the environment.
Key Point: Understanding these variables is crucial for designing and interpreting the results of a scientific investigation.
