ACT (Enhanced)ScienceEasy
A student is investigating the effect of different pH levels on the growth of a specific type of mold. They prepare five petri dishes, each containing the same amount of nutrient agar. Dish 1 has a pH of 4, Dish 2 a pH of 5, Dish 3 a pH of 6, Dish 4 a pH of 7, and Dish 5 a pH of 8. All dishes are inoculated with the same amount of mold spores and incubated at 25°C for 7 days. Which of the following would be the most appropriate dependent variable to measure in this experiment?
- AThe temperature of incubation for each petri dish.
- BThe diameter of the mold colony in each petri dish after 7 days.
- CThe initial amount of mold spores inoculated in each dish.
- DThe pH level of the nutrient agar in each petri dish.
Show answer & explanationAnswer & explanation
Correct answer: B. The diameter of the mold colony in each petri dish after 7 days.
The dependent variable is the factor that is measured or observed and is expected to change in response to the independent variable. In this experiment, the independent variable is pH, and the growth of the mold is what is being measured.
Why the other options are wrong
- A. This is a controlled variable, not the dependent variable, as it is kept constant.
- C. This is a controlled variable, not the dependent variable, as it is kept constant.
- D. This is the independent variable, the factor being intentionally changed by the experimenter.
Dependent Variable
The variable in an experiment that is measured or observed by the researcher. Its value is expected to change in response to the independent variable.
- It's the 'effect' in a cause-and-effect relationship.
- It is measured or observed.
- Its value depends on the independent variable.
Memory trick: Independent Causes Dependent Change, Controls Stay Same