Overview
This lecture explains the three types of variables in scientific experiments and why controlling variables is essential to obtain meaningful results.
Types of Variables in Experiments
- Variables are factors that can change or vary in an experiment.
- There are three types of variables: independent, dependent, and controlled.
Independent Variable
- The independent variable is what the experimenter changes or manipulates.
- In the squid experiment, the independent variable is the amount of vitamins given to the squid.
- Only one independent variable should be tested in a good experiment.
Dependent Variable
- The dependent variable is what is measured in the experiment (the results).
- In the squid experiment, the dependent variable is the squid’s lifespan.
- The dependent variable changes in response to the independent variable.
Controlled Variables
- Controlled variables are factors kept constant to ensure a fair test.
- Examples of controlled variables in the squid experiment are temperature, food type, and water quality.
- All variables except the independent variable must be controlled to draw valid conclusions.
Importance of Controlling Variables
- If controlled variables are not kept constant, experimental results become meaningless.
- Uncontrolled variables can introduce other explanations for the outcome, making it impossible to determine the effect of the independent variable.
Key Terms & Definitions
- Variable — Anything that can vary or change in an experiment.
- Independent Variable — The factor deliberately changed by the experimenter.
- Dependent Variable — The factor measured as the outcome of the experiment.
- Controlled Variable — Any condition that is kept constant across experimental groups.
Action Items / Next Steps
- Make sure to identify and control all variables except the independent variable in your own experiments.