ACT (Enhanced)ScienceMedium
A researcher conducts an experiment to test the effectiveness of a new fertilizer on plant growth. They divide 60 identical plants into three groups: Group A (control, no fertilizer), Group B (low concentration fertilizer), and Group C (high concentration fertilizer). All other conditions (light, water, soil type) are kept constant. After four weeks, the average height of plants in each group is measured. Which of the following would constitute a valid control group for this experiment?
- AA group of plants receiving varying amounts of water.
- BGroup B, receiving low concentration fertilizer.
- CGroup A, receiving no fertilizer.
- DA group of plants grown in different soil conditions.
Show answer & explanationAnswer & explanation
Correct answer: C. Group A, receiving no fertilizer.
A control group serves as a baseline for comparison, receiving no treatment or the standard treatment. In this case, Group A, which receives no fertilizer, allows the researcher to see the natural growth of the plants without the experimental variable.
Why the other options are wrong
- A. This group introduces another variable (water), making it unsuitable as a control for fertilizer effectiveness.
- B. This is an experimental group, testing a specific fertilizer concentration.
- D. This group introduces another variable (soil type), making it unsuitable as a control for fertilizer effectiveness.
Control Group
A group in an experiment that does not receive the treatment or manipulation being tested, serving as a baseline for comparison.
- Essential for establishing cause-and-effect relationships.
- Helps isolate the effect of the independent variable.
- All other conditions should be identical to experimental groups.
Memory trick: The 'Control' is the comparison, the 'no change' group.