1. Independent Variable (IV):
* Definition: The variable that the experimenter *manipulates* or changes. It's the factor that is believed to have an effect on the outcome.
* Example: In an experiment testing the effect of fertilizer on plant growth, the independent variable is the amount of fertilizer applied.
2. Dependent Variable (DV):
* Definition: The variable that is *measured* in an experiment. It's the outcome that is being observed or recorded.
* Example: In the fertilizer experiment, the dependent variable is the height of the plants.
3. Controlled Variables (CV):
* Definition: Variables that are kept *constant* throughout the experiment to ensure that the results are due to the independent variable, not other factors.
* Example: In the fertilizer experiment, controlled variables could include:
* Type of plant used
* Amount of water given
* Sunlight exposure
* Temperature of the environment
4. Extraneous Variables (EV):
* Definition: Variables that could potentially *influence* the results but are not being studied in the experiment. They are often difficult to control.
* Example: In the fertilizer experiment, an extraneous variable could be the presence of pests that might affect plant growth.
5. Confounding Variables:
* Definition: A type of extraneous variable that is *related to* the independent variable and can *distort* the results, making it difficult to determine if the independent variable is truly responsible for the observed effect.
* Example: In a study on the effect of a new drug on blood pressure, a confounding variable could be the patients' existing health conditions (e.g., pre-existing high blood pressure).
Important Note:
* Experimentation is about isolating the effect of the independent variable. By carefully controlling other variables and accounting for extraneous ones, researchers can make more confident conclusions about the relationship between the independent and dependent variables.
