ACT (Enhanced)ScienceEasy
A marine biologist is studying the growth rate of a specific type of coral under varying ocean acidification conditions. They set up several tanks, each with a different pH level (7.8, 8.0, 8.2, 8.4). All other factors, such as temperature, light, and nutrient levels, are kept constant across all tanks. Coral growth is measured weekly. In this experiment, what is the independent variable?
- AThe pH level of the water.
- BThe type of coral being studied.
- CThe temperature of the water.
- DThe growth rate of the coral.
Show answer & explanationAnswer & explanation
Correct answer: A. The pH level of the water.
The independent variable is the factor that is intentionally changed or manipulated by the experimenter to observe its effect on another variable. In this case, the pH level is being varied by the biologist.
Why the other options are wrong
- B. The type of coral is constant, making it a controlled variable, not the independent variable.
- C. Temperature is stated as being kept constant, making it a controlled variable, not the independent variable.
- D. This is the dependent variable, as it is measured in response to changes in pH.
Independent Variable
The variable that is changed or controlled in a scientific experiment to test its effects on the dependent variable.
- It is manipulated by the researcher.
- Its changes are presumed to cause changes in the dependent variable.
- Often denoted as 'x' in graphs.
Memory trick: Independent is what I change, Dependent is what's measured.