Overview
This lecture explains independent, dependent, and controlled variables using an experiment on the effect of sunlight on plant growth.
Identifying Variables in Experiments
- The experiment tests if sunlight affects plant growth.
- Sunlight is the independent variable because it is changed by the experimenter.
- Plant growth is the dependent variable because it is affected by the amount of sunlight.
Relationship Among Variables
- The independent variable (sunlight) can cause changes in the dependent variable (plant growth).
- There is a cause-and-effect relationship: sunlight (cause) influences plant growth (effect).
Experimental and Controlled Setups
- Experimental setup includes plants exposed to sunlight (independent variable is present).
- Controlled setup has plants with no sunlight (independent variable is absent).
- Both setups keep all other conditions the same (e.g., plant species, soil, pot size, water amount).
Controlled Variables
- Controlled variables are all kept constant except for the independent variable.
- These ensure that only sunlight affects plant growth, supporting accuracy and reliability.
Observation and Results
- The dependent variable (plant growth) is what is measured during the experiment.
- After one month, plants with sunlight grow, while those without sunlight die, showing dependency.
Key Terms & Definitions
- Independent Variable — the variable changed by the experimenter; the "cause" in the experiment.
- Dependent Variable — the variable that changes as a result of the independent variable; the "effect" observed.
- Controlled Variable — variables kept the same in all setups to ensure a fair test.
- Experimental Setup — setup where the independent variable is present.
- Controlled Setup — setup identical to the experimental setup but without the independent variable.
Action Items / Next Steps
- Review definitions and examples of independent, dependent, and controlled variables.
- Practice identifying these variables in new experimental scenarios.